MediaProvider: Avoid issue of android.process.media stop

"OK" and "Cancel" button's click event response at the same time
lead to FATAL EXCEPTION. Make the click events do not happen at
the same time.

Change-Id: I92fc1dc15be42d0bd9fe54f41fdbb26b3ca4b85c
CRs-Fixed: 513752
Merge "MediaProvider: Avoid issue of android.process.media stop" into du44