audiopolicy : Fix for incorrect input device selection

Some VoIP applications do not use source as VOICE_COMM
but MIC and policy manager ignores the force usage in that
case and selects handset-mic as input device even when
BT-SCO headset is connected.
Check the force usage for the AUDIO_SOURCE_MIC as well.

Bug: 18606571

Change-Id: I5d5010ab396f85bf58573943c91fd815f39f57c1