IMS: Handle USER_* messages in Quiescent* states.

Currently USER_* requests are only handled in Active*
states of CallAudioRouteStateMachine which in some
cases results in ignoring user requests. This change
modifies Quiescent* states to handle USER_* messages
similiar to corresponding none-user initiated messages.

BUG=28602331
Change-Id: I1ec932b8961ed74956c81a2ccd448b7b9fbb6dca
1 file changed