SCO: Suspend and resume A2DP before SCO setup and after SCO tear down

* Suspend A2DP:
  - before calling mNativeInterface.connectAudio(device)
  - before call state becomes busy and audio should be connected, as defined by:
    1. numActive + numHeld > 0
    2. Call setup state is not idle, but not incoming
    3. Call state is incoming and in-band ringing is enabled
* Resume A2DP:
  - when mNativeInterface.connectAudio(device) returns false
  - when SCO audio is disconnected and call state is idle as defined by:
    1. numActive + numHeld > 0
    2. Call setup state is not idle

Bug: 74988740
Test: make a hangout call while music is playing
Change-Id: I85672b4e61c91a7db2458600ad3bacfe8d529af1