Fix RemoteException handling in MediaController

As per go/android-api-guidelines#framework-rethrow-remoteexception, we
should strongly rethrow any RemoteException coming from system_server.

Bug: 205124386
Test: Presubmit.
Flag: EXEMPT bugfix: Low risk change to improve behavior in an already crashing system.
Change-Id: I1f8b3f3e201d7d2f41bb9e1ae5dd3969896b5bd7