Suspend A2DP only when HFP has the active device

There is no reason to suspend A2DP because SCO will never be used
without HFP active device.

Bug: 185191975
Tag: #compatibility
Test: atest BluetoothInstrumentationTests:com.android.bluetooth.hfp
Change-Id: Ifeade77391d20df3348a93c90f1eea8899069fce
Merged-In: Ifeade77391d20df3348a93c90f1eea8899069fce
(cherry picked from commit 21f29963)