OPENDJ-1190 (CR-2523) Under rare circumstances the DS replication recovery thread (RSUpdater) can spin


This change is linked to the misbehaving RSUpdater thread which (wrongly):
- could be started multiple times
- would not shutdown willingly when the server is shutting down
- would try to look for replay operations in the future



LDAPReplicationDomain.java:
In now(), ensured now() will always come last with isNewerThan() test.