Unregister user switch observer in ActivityManagerShellCommand.

ActivityManagerShellCommand does not unregisterUserSwitchObserver
after registerUserSwitchObserver, which leads to a leak of
unnecessary callbacks. This CL adds unregistering in finally block.

Bug: 242176088
Test: Manual test with adb and perfetto.
Change-Id: I14d66a00c5dd3f881d393a386a2678835c99a900
1 file changed