Cover cmd-exclude-prefixes-k8s by integration tests

[denis-tingaikin]

Description

We've completed cmd-exclude-prefixes-k8s and now we can cover the application by integration tests.

Test scenarios

We need to cover the next scenarios:

1. Verify that cmd-exclude-prefixes-k8s can correctly read cluster prefixes from kube-system configmap.
2. Verify that cmd-exclude-prefixes-k8s can correctly collect prefixes if configmap from scenario1 is missed.
3. Verify that cmd-exclude-prefixes-k8s can correctly read user's prefixes
   3.1. Verify deleting the user's prefixes.
   3.2. Verify updating the user's prefixes.
   3.3. Verify adding the user's prefixes.
4. Verify that cmd-exclude-prefixes-k8s can correctly read prefixes from envs.
   4.1. Verify that cmd-exclude-prefixes-k8s is working fine with correct prefixes from envs.
   4.2. Verify that cmd-exclude-prefixes-k8s is failing with incorrect prefixes from envs.
5. Verify collision prefixes collision cases.

Testing notes

We have not completed tests for nsmgr + nsc yet, and for first step we can collect prefixes into alpine pod via shared volume. And check file source via kubectl cp, kubectl exec -ti "pod name" -- cat "path".

[denis-tingaikin]

@tigrulya-exe cc

[Mixaster995]

closed in favor of networkservicemesh/deployments-k8s#1353