Code cleanup.


MessageHandler.java:
Removed instance members replicationServerId and replicationServerURL from the classes in org.opends.server.replication.server package (duplicated information already held on replicationServer).
Added getReplicationServerURL().

ECLServerHandler.java:
Removed duplicated code in ctors.
In getNextECLUpdate(), tried to simplify reading of the code.

*.java:
Changed code as a consequence of the changes to MessageHandler.
Made some fields private.
In getMonitorData(), changed return type from ArrayList to List.