Fix pre command flags

[spowelljr]

Fixes #13994

Problem:
Having a flag before the command (ex. minikube --alsologtostderr start) would break instances that were coded to look for the command using os.Args[1]. This would result in issues such as not creating a lastStart.txt and not properly detecting if a purge delete was occurring.

Solution:
Replaced instances of os.Args[1] with pflag.Arg(0). pflag.Arg returns all args from os.Args[1:] that aren't flags, resulting in only true args (ex. minikube --alsologtostderr start --driver docker -> pflag.Args() = ["start"]). pflag.Arg() will also return an empty string if trying to access a non-existing arg index.

[sharifelgamal]

/ok-to-test

[minikube-pr-bot]

kvm2 driver with docker runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 13995) |
+----------------+----------+---------------------+
| minikube start | 51.8s    | 51.6s               |
| enable ingress | 32.0s    | 29.4s               |
+----------------+----------+---------------------+

Times for minikube start: 55.9s 50.8s 50.3s 50.4s 51.4s
Times for minikube (PR 13995) start: 52.8s 51.0s 51.1s 51.1s 52.0s

Times for minikube ingress: 30.8s 38.6s 30.6s 30.0s 30.1s
Times for minikube (PR 13995) ingress: 30.2s 29.1s 29.5s 31.0s 27.1s

docker driver with docker runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 13995) |
+----------------+----------+---------------------+
| minikube start | 25.7s    | 24.5s               |
| enable ingress | 23.6s    | 23.9s               |
+----------------+----------+---------------------+

Times for minikube ingress: 24.4s 22.9s 23.9s 24.0s 22.9s
Times for minikube (PR 13995) ingress: 23.0s 23.4s 23.4s 27.0s 22.9s

Times for minikube start: 28.9s 24.9s 25.3s 24.5s 24.7s
Times for minikube (PR 13995) start: 25.5s 25.3s 23.8s 24.2s 23.6s

docker driver with containerd runtime

+----------------+----------+---------------------+
|    COMMAND     | MINIKUBE | MINIKUBE (PR 13995) |
+----------------+----------+---------------------+
| minikube start | 41.8s    | 41.8s               |
| enable ingress | 19.9s    | 23.7s               |
+----------------+----------+---------------------+

Times for minikube ingress: 17.9s 17.9s 17.9s 17.9s 27.9s
Times for minikube (PR 13995) ingress: 18.4s 21.9s 27.9s 21.9s 28.4s

Times for minikube (PR 13995) start: 43.7s 39.3s 43.8s 39.4s 42.9s
Times for minikube start: 33.4s 43.8s 44.0s 43.7s 44.2s

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sharifelgamal, spowelljr

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