Binary for mtu and veth prefix check

[cgchinmay]

What type of PR is this?
Added binary support for validating mtu and veth prefix for aws-node daemonset

Which issue does this PR fix:
Ginkgo test won't have to run exec commands, instead they can invoke this binary to validate mtu and veth prefix

What does this PR do / Why do we need it:
To facilitate ginkgo testing

Testing done on this change:

/tmp # ./aws-node-config --help
Usage of ./aws-node-config:
  -mtu-val int
    	Expected MTU values, specify when validating mtu (default 9001)
  -prefix string
    	veth prefix to be used, specify when validating veth (default "eni")
  -validate string
    	name of the test, valid values: mtu, veth
  -veth-count int
    	Number of expected veth links to have the new prefix. specify when validating veth (default 1)
/tmp # 
/tmp # 
/tmp # ./aws-node-config --validate mtu -mtu-val 1300
2021/05/06 20:33:36 MTU Check: Passed
/tmp # ./aws-node-config --validate mtu -mtu-val 9001
2021/05/06 20:33:43 MTU Check: Failed
/tmp # 
/tmp # 
/tmp # 
/tmp # 
/tmp # ./aws-node-config --validate veth -prefix veth -veth-count 2
2021/05/06 20:34:33 Veth Check: Failed
/tmp # ./aws-node-config --validate veth -prefix eni -veth-count 2
2021/05/06 20:34:41 Veth Check: Passed

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[abhipth]

LGTM!