The ReplicationLogCleaner is not thread safe but can be called from different threads at the same time

In preClean method we will update the class fields and then use them in the getDeletableFiles method. This implies that we will have only one cleaner run at the same time.

But actually, in MasterRpcServices.runCleanerChore, we will call execute the HFileCleaner and LogCleaner directly, not in the cleanerChore thread.

This could cause data loss for replication, which is a very serious problem.