FM Radio: do not try to change thread priority

The FM Radio services try to change the current thread when
instantiated, for unknown reason. This actually ends up changing the
priority of SystemServer's main thread. Probably a bad idea. This is
the cause of the various glitch fallout after the FM Radio merges.

Change-Id: I292aff3380c717ff1bc7d45f6303c0d330ef642d