CEC: Queue up callbacks to handle on final result

While one party calls oneTouchPlay() to initiate the action and
put it in progress, the other parties making the same call gets
an error 'operation in progress'. This is not really an error,
but there was no other choice for them but just to wait till
the action is completed and the service is ready to accept
the API call again.

This CL resolves the inconvenice by allowing multiple callbacks
rather than returning IN_PROGRESS for those joining later. Same
was applied to queryDisplayStatus().

Change-Id: I5fc9aba4aa73e76a25f8fdec37e11cd961a3d35f
(cherry picked from commit 98a25f1ee27c1b4362a23981edc17fc92199a876)