audio: Update anchor time only when sink start is successful

- During offload (WH) to non-offload fallback (BT),
  anchor time is getting updated incorrectly with
  offload renderer position when it tries to start
  sink using offload mode only.

- update anchor time post resume only when sink is
  started successfully.

Change-Id: I2c2992afa90506e08389226964b0bd5a5be07529
CRs-Fixed: 978596