Fix TerminationMonitor to reference correct Monitor class
The TerminationMonitor actor listens for messages of type
org.opendaylight.controller.cluster.datastore.messages.Monitor
but the AbstractUntypedActor sends a message of type
org.opendaylight.controller.cluster.common.actor.Monitor.
TerminationMonitor was changed to reference the right class and
org.opendaylight.controller.cluster.datastore.messages.Monitor was
removed.
Change-Id: Ie0e8dd4face529c3b40e1227fec575a8bd4c9425
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>