NPM doesn't work with Patched Kubernetes

[robbiezhang]

Is this a request for help?:
Yes

Is this an ISSUE or FEATURE REQUEST? (choose one):
Issue

Which release version?:
1.0.29 or above

Which component (CNI/IPAM/CNM/CNS):
NPM

Which Operating System (Linux/Windows):
Linux

For Linux: Include Distro and kernel version using "uname -a"
Any

For windows: provide output of "$(Get-ItemProperty -Path "C:\windows\system32\hal.dll").VersionInfo.FileVersion"

---

Which Orchestrator and version (e.g. Kubernetes, Docker)
Kubernetes

What happened:
Bug in parsing the k8s version:

azure-container-networking/npm/util/util.go

Lines 101 to 105 in aeacc60

	v1, err := semver.NewVersion(firstVer.Major+firstVer.Minor)
	if err != nil {
	return -2
	}
	v2, err := semver.NewVersion(secondVer.Major+secondVer.Minor)

In a patched k8s, the version.Info apiserver returns looks like

version.Info{
Major: "1",
Minor: "14+",
GitVersion: "1.14.8-hotfix.20200127",
}

While "14+" is not a valid semver, since it only allows number identifier in the minor. https://semver.org/#spec-item-11
The current code to semver.NewVersion(Major+Minor) will get a semantic error.
https://play.golang.org/p/7j2Dcx5_fpH

Further, Major+Minor comes up with "111" for 1.11, which has potential issue if k8s start to bump up the Major version (111 > 21).

---

What you expected to happen:
NPM should work with patched kubernetes apiserver.

How to reproduce it (as minimally and precisely as possible):
Build k8s cluster (AKS-Engine)
Replace the apiserver image by mcr.microsoft.com/oss/kubernetes/hyperkube:v1.14.8_f0.0.3
Install the NPM 1.0.30
You will find NPM pod crash with the following error message:

azure-container-networking/npm/npm.go

Line 223 in aeacc60

log.Logf("Error: failed to set IsNewNwPolicyVerFlag")

If you run kubectl version, you will get the following version information.
Server Version: version.Info{Major:"1", Minor:"14+", GitVersion:"v1.14.8-hotfix.20200127", GitCommit:"c52f59bbba5fbf21fbb18e9a06f96e563fe4c20a", GitTreeState:"clean", BuildDate:"2020-01-28T02:47:05Z", GoVersion:"go1.12.10", Compiler:"gc", Platform:"linux/amd64"}

---

Anything else we need to know:
I'd propose to use the GitVersion to get the k8s version.