Nowadays, it can only deadlock (threads>0) or do nothing (threads==0)

This reverts commit d4485423.

Should fix a crash reported by the bugreport ml.

audioscrobbler: *Never* do module unloading from within the module. You are basically unloading the code you are executing, that's a nice crasher.

Also make sure playlist is not NULL. (This is an attempt to fix a from the famous bugreport ml).

The audio output locking rule seems very vague. Moreover there could be some cross lock issues.

Spotted in our bugreport ml.