audio_policy: Fix for audio routing to speaker though BT is connected

- When voice dialer is active and play is issued from the connected
  BT headset, audio is heard on speaker.
- Speaker is selected in getDeviceForStrategy() although BT is connected
  as the flag 'mA2dpSuspended' remains 'true'. The flag is not updated in
  checkA2dpSuspend() as force usage for communication
  and record remains FORCE_BT_SCO as voice dialer is active.
- Modify the conditional check to set the flag to 'false'.

Change ported from I86ebb66cd165e8009bfa6193d2ad9ab383996283

CRs-Fixed: 750370
Change-Id: Ie6fd9a552386465390b10168f878dfceb82aa86b