audioflinger: change session check in createTrack.

Do not refuse to create a track on an output thread if the same session
is present on another thread. It is now possible that two tracks
with the same session ID are on different threads if one can use deep
buffering and the other can't.

In this case, move effects attached to this session to the output
thread ion which the new track is created.

Bug 6530324.

Change-Id: I9019b3ee382e374c89d2319033afcfa7f886e4c4