Forbid remove all controllers at once

We need to forbid remove all controllers even you add new one at the
same time, since it affects cluster's availability.

(cherry picked from commit ac23dc36eecbcbb5aba202dbcc63fbf774149dae)

Change-Id: I9d1ac51981d0516937aa21e04e66e2cca03022ef
Closes-Bug: #1367001
Merge "Forbid remove all controllers at once" into stable/5.1