Derive MockRaftActorContext from RaftActorContextImpl
I changed MockRaftActorContext to derive from RaftActorContextImpl since
it duplicates most of the functionality in RaftActorContextImpl and,
with the addition of PeerInfo, MockRaftActorContext can now provide the
same functionality as RaftActorContextImpl w/o having to duplicate it in
MockRaftActorContext. Also this will make it easier when the RaftActorContext
interface is changed.
Change-Id: Ief90232fc992a50b3f0fea5ece323a14916760f2
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>