audio: avoid mute delay when no active stream

-Dialpad touch tone delay is observed when connected USB
 headset. This is beacuse of mute delay during  device switch
-In this usecase, mute delay is not required as there is no
 actual device switch
-Fix is to avoid delay in this usecase.

Change-Id: Ib9e7d7f953f740c9f96c43a104edd0b548421e8d
CRs-Fixed: 706678