Add e2e tests for operator

[amuraru]

Is your feature request related to a problem? Please describe.

Add e2e tests for operator

Describe the solution you'd like to see

The solution should allow running the e2e tests from a dev box and in a CI environment We can burrow the idea of integrating kind and go tests from our friends at Improbable: https://github.com/improbable-eng/etcd-cluster-operator/blob/master/internal/test/e2e/e2e_test.go

[panyuenlau]

@hong6914 FYI about this e2e testing request from the community

[hong6914]

Thank you --- an internal JIRA ticket was created to track the progress.