The implementation for AudioManager.setMicrophoneMute() used to
call directly into AudioSystem which called directly into
AudioFlinger and the mediaserver process, where the check for
the MODIFY_AUDIO_SETTINGS is performed.
A regression was introduced by Ib32138bcc256cfbac4fe21a090d5ba34f5c641fc
which calls first into AudioService which runs in system_process
before calling into AudioSystem, which granted the permission.
This CL adds a permission check in this code path when calling
AudioService.
Bug 17259652
Change-Id: I4ac5269262eb90df80ee81db6ec3d96977ee53be
4a4fea0752