Camera2: Synchronize access to camera parameters

- Concurrent access between the main handler
  thread and the camera start-up thread w.r.t.
  'mParameters' is possible. This change will
  synchronize the two threads in order to avoid
  any exceptions.

( cherrypicked from commit e988411c441410f270fe0b98dfd0d9b1f033503f )

Change-Id: I290452723b3687eba5240f451cc94aef175a9fc4
CRs-Fixed: 539634