Implement ChangeServersVotingStatus message in RaftActor
Backported from master.
Added a new ChangeServersVotingStatus message to change servers to/from
voting members. The leader updates its local peer info and persists and
replicates a new ServerConfigurationPayload with the appropriate voting
states. If the leader changes to non-voting it steps down as leader by
initiating a leadership transfer.
Change-Id: If073e4665cb1a270aae6e3dce36a6b3e900d0282
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>