Add permission check on onKeyguardVisibilityChanged

Without this permission check any app can toggle the locked state of
keymaster once it has been unlocked for the first time.

Bug: 144285084
Test: Manually tested with debugger that the requred code paths are
      run.

Change-Id: Idb8a200dc2963e1085e9fddd0c565c5172465e65
1 file changed