Remove reuse of pending deferred transactions.

Only defer transactions originating from repositionChild. There is
no guarantee the frame we are suggested to synchronize to will ever
arrive and synchronizing WM originated transactions to this can
interfere with implementation of system policy. Anyway this code
originally was fixing a case where transactions pushed by pulling
down the notification shade, would interrupt animating SurfaceView's
by pushing an undeferred transaction for those SurfaceView's. This
doesn't seem to be occuring anymore even without this code. Furthermore
even if it was occuring, we should prevent transactions from pushing
updates for Surfaces where nothing has really changed, rather than
attempt to chain the deferred transactions.

Bug: 31293950
Bug: 27098060
Bug: 28858420
Change-Id: Ifb83fe78bb4e7d18376e53a743709648aa1e03bc