Change start/stop lock-task-mode to two way binder

There could be a timing that the #finishActivity is done before
#stopLockTaskModeByToken, even the client requested the lock-task
to be stopped before finishing the activity, which prevents the
Activity to be finished.

Bug: 370362798
Test: wm presubmit
Flag: EXEMPT bugfix
Change-Id: Ic35cc4903f41b185a8bb9f6a0880fe4df933999b