Fix deadlock in MountService

It is not safe to call into vold with a lock held on mVolumeStates
since we will receive events back from vold on a different thread.
So in the boot completed handler we make a copy of the volume list and
then call vold to mount volumes after releasing the lock

Change-Id: I0dee91f09e4056132aaaf0fb0a663148c65db1e4
Signed-off-by: Mike Lockwood <lockwood@android.com>