Enabling ASYM_ENCRYPT#change_key_on_leave logs "unrecognized cipher; discarding message from X" during normal operation

The problem is in design, when a message with out of date key is received, its dropped and retransmitted with the new key, however, logging the "WARN [org.jgroups.protocols.ASYM_ENCRYPT] (thread-3,null,null) Y: unrecognized cipher; discarding message from X".

Unless a better solution is implemented, the least we could do, is improve the message to indicate this is part of normal operation.