Skip locking focus_state mutex if sound_manager_get_focus_state() is called in focus...

Skip locking focus_state mutex if sound_manager_get_focus_state() is called in focus callback

During destroying handle, it is possible that the focus state callback is
called simultaneously. The destroy function already lock the mutex also,
deadlock can occur if user calls the sound_manager_get_focus_state() function
inside of the focus state callback context. It is now fixed with this patch.

[Version] 0.6.39
[Issue Type] Improvement

Change-Id: I092d127fb8e29dc5fea0056d3b4f1da101130f3d
Signed-off-by: Sangchul Lee <sc11.lee@samsung.com>