AudioFlinger: mute mic on primary HAL only

Only the primary HAL has to support mic mute function.
Ignore errors returned by other HALs in setMicMute() and
only report mic mute state from primary HAL in getMicMute().

Bug: 153103117
Test: CTS AudioManagerTest.testMicrophoneMute
Test: manual phone call and verify microphone mute.
Change-Id: Ic121c49e7e7cd75eeee9342249271c7fca7c1c2a