[replication] minor code bug when registering ReplicationLogCleaner

We try to register ReplicationLogCleaner by default. This is done by calling Replication.decorateMasterConfiguration()in the master.

In the current Replication.decorateMasterConfiguration():
...
String plugins = conf.get(HBASE_MASTER_LOGCLEANER_PLUGINS);
if (!plugins.contains(ReplicationLogCleaner.class.toString()))

{ conf.set(HBASE_MASTER_LOGCLEANER_PLUGINS, plugins + "," + ReplicationLogCleaner.class.getCanonicalName()); }

...

ReplicationLogCleaner.class.toString() will return prefix 'class' to the full class name, which will make the if checking mostly useless.