[MediaProjection] Finish permission activity if dialog dismissed or cancelled

Currently, when turning off/turning on the screen
the activity still stays visible. We handle the dialog
cancellation case by finishing the activity in onCancel
callback but we don't do this for dismissing.

Bug: 276431368
Test: open media projection dialog, turn off the screen,
  turn on the screen => check that dialog and activity
  are dismissed and closed
Change-Id: I17b8a26e0285fab7b99871290a1588a5b6b13cfa