AudioService: do not use virtual call for bt sco

Do not use startScoUsingVirtualVoiceCall() BluetoothHeadset
API to connect SCO audio. This will cause headsets to act as if an incoming
call was received which is not what we want for voice commands.

Bug 8157702

Change-Id: I271909d4d1f3822758740a8484e3d2d8b4f34c00