Fix multithread issue in localmsg API

I'm afraid this solution isn't going to work correctly with MIDlets that define custom localmsg servers. For example, I think a scenario with two clients that connect to a server won't work (the second client that tries to connect will find _cachedFakeLocalMsgConnections.length == 0)
(The name of the variable should also be changed, since these servers are the only ones that weren't implemented by us via reverse engineering :smile: )