Fixed the failing nightly test GenerationIdTest.testSingleRS().


GenerationIdTest.java:
In testSingleRS(), called again ReplicationServer.remove() instead of ReplicationServerTestCase.remove() because the test does not expect the DB to be wiped out.
Changed all protected keywords to private since it is never subclassed.
Renamed testEntriesInDb() to countUpdatedEntriesInDb().
Removed useless try / catch and let the exceptions go up.
Replaced uses of assertTrue() with the appropriate assert* method.
Changed the return type of createAddMsg() to return the appropriate type.
Extracted method assertNoMessageReceivedBadGenId(), waitForStableGenerationId().

ReplicationTestCase.java:
In addTestEntriesToDB(), used varargs.
Removed outdated openReplicationSession().
Removed useless try / catch and let the exceptions go up.

ReplicationServerTest.java:
Extracted method sendAndReceiveDeleteMsg() and newServerState().
Used Arrays.asList().