Automatic merge from submit-queue

Fixed e2e tests for HA master.

Set of fixes that allows HA master e2e tests to pass for removal/addition master replicas.

The summary of changes:
- fixed host name in etcd certs,
- added cluster validation after kube-down,
- fixed the number of master replicas in cluster validation,
- made MULTIZONE=true required for HA master deployments, ensured we correctly handle MULTIZONE=true when user wants to create HA master but not kubelets in multiple zones,
- extended verification of master replicas in HA master e2e tests.