In the past MUCController added a "trying to enter..." message and later tried to replace this with "entered room as..." message. However, any message received in between, like a system message about room topic, came in between since MUCController replaced the *last* message added to the log. The new code also adds message IDs to system messages. This way the correct message can be replaced on successful login, no matter how many messages came in between. Test-Information: Tested against a MUC component that send a system message before sending the join presence back to a user. Change-Id: I3bcb5d78de680494965d837b2ad3edb847ff7f99