fix: "compose service up" sets desired count to 1

[SoManyHs]

Previously, we would first call CreateService with desired count 0 then
call UpdateService to set the desired count to 1. This eliminates extra
API calls, as well as the need to wait until the service is describable
before "starting" it.

Note: This effectively reverts 264fe13

Related: #79

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[SoManyHs]

Compose service up now creates service with desired count = 1:

$ ecs-cli --version
ecs-cli version 1.18.0 (*41b3dc2)

$ ecs-cli compose service up
INFO[0000] Using ECS task definition                     TaskDefinition="test_fields:72"
INFO[0000] Created an ECS service   

$ aws ecs describe-services --region us-west-2 --service test_fields
{
    "services": [
        {
            "status": "ACTIVE", 
            "serviceRegistries": [], 
            "pendingCount": 0, 
            "launchType": "EC2", 
            "enableECSManagedTags": false, 
            "schedulingStrategy": "REPLICA", 
            "loadBalancers": [], 
            "placementConstraints": [], 
            "createdAt": 1582576760.559, 
            "desiredCount": 1, 
            "serviceName": "test_fields", 
            "clusterArn": "arn:aws:ecs:us-west-2:xxxxxxx:cluster/default", 
            "taskDefinition": "arn:aws:ecs:us-west-2:xxxxxxxx:task-definition/test_fields:72", 
            "serviceArn": "arn:aws:ecs:us-west-2:xxxxx:service/test_fields", 
            "propagateTags": "NONE", 
            "deploymentConfiguration": {
                "maximumPercent": 200, 
                "minimumHealthyPercent": 100
            }, 
            "deployments": [
                {
                    "status": "PRIMARY", 
                    "pendingCount": 0, 
                    "launchType": "EC2", 
                    "createdAt": 1582576760.559, 
                    "desiredCount": 1, 
                    "taskDefinition": "arn:aws:ecs:us-west-2:xxxxxxxx:task-definition/test_fields:72", 
                    "updatedAt": 1582576785.549, 
                    "id": "ecs-svc/4901267662372024888", 
                    "runningCount": 1
                }
            ], 
            "events": [
                {
                    "message": "(service test_fields) has reached a steady state.", 
                    "id": "52395df6-cdcc-44a8-a85b-f9d4f7ab91b4", 
                    "createdAt": 1582576785.557
                }, 
                {
                    "message": "(service test_fields) has started 1 tasks: (task 64b69c58-6ed3-4c3f-a4e6-5c8bdc5bd552).", 
                    "id": "de52edbb-f4ca-40ea-98fb-40bd4268f7c8", 
                    "createdAt": 1582576764.429
                }
            ], 
            "runningCount": 1, 
            "placementStrategy": []
        }
    ], 
    "failures": []
}

[SoManyHs]

Previous behavior (made two separate API calls):

~/ecs/ecs-cli/testing/projects/test_fields(master)$ ecs-cli --version
ecs-cli version 1.18.0 (*26c7177)

~/ecs/ecs-cli/testing/projects/test_fields(master)$ ecs-cli compose service up
INFO[0000] Using ECS task definition                     TaskDefinition="test_fields:72"
INFO[0000] Created an ECS service                        service=test_fields taskDefinition="test_fields:72"
INFO[0000] Updated ECS service successfully              desiredCount=1 force-deployment=false service=test_fields
INFO[0015] Service status                                desiredCount=1 runningCount=1 serviceName=test_fields
INFO[0015] (service test_fields) has started 1 tasks: (task 4c9d2052-7bd7-4e2c-8b28-7ae655ccb5ac).  timestamp="2020-02-24 20:45:37 +0000 UTC"
INFO[0015] ECS Service has reached a stable state        desiredCount=1 runningCount=1 serviceName=test_fields

[uttarasridhar]

Reading the documentation for the up command:
Creates an Amazon ECS service from your compose file (if it does not already exist) and runs one instance of that task on your cluster (a combination of the create and start commands). This command updates the desired count of the service to 1.
Can we make sure the command is idempotent in the sense that if customers run compose service create and follow it with compose service up it should succeed.

This might require us to check for ServiceAlreadyExists Error in line 249 and call updateService instead

[efekarakus]

Can we make sure the command is idempotent in the sense that if customers run compose service create and follow it with compose service up it should succeed.

I believe we'll go inside if the if-block iff the service does not exist or is inactive.
If the service already exists then l. 253 updateService is invoked.

So the behavior of the command should still be like before :)

[SoManyHs]

@uttarasridhar

$ ecs-cli --version
ecs-cli version 1.18.0 (*41b3dc2)

$ ecs-cli compose service create
INFO[0000] Using ECS task definition                     TaskDefinition="test_fields:72"
INFO[0000] Created an ECS service                        service=test_fields taskDefinition="test_fields:72"

$ aws ecs list-services --region us-west-2 
{
    "serviceArns": [
        "arn:aws:ecs:us-west-2:xxxxxx:service/test_fields"
    ]
}

$ ecs-cli compose service up
INFO[0000] Using ECS task definition                     TaskDefinition="test_fields:72"
INFO[0000] Updated ECS service successfully              desiredCount=1 force-deployment=false service=test_fields
INFO[0015] Service status                                desiredCount=1 runningCount=1 serviceName=test_fields
INFO[0015] (service test_fields) has started 1 tasks: (task b24f3e4b-d190-487f-a8ad-5faa44e00ffa).  timestamp="2020-02-25 01:06:19 +0000 UTC"
INFO[0015] ECS Service has reached a stable state        desiredCount=1 runningCount=1 serviceName=test_fields