audioflinger: fix invalidateTracks() on offload thread am: 1308462107 am: 514d8c512d
am: a043ba313b

* commit 'a043ba313b68a7e6694b17faaca7f10dd4e5f1d2':
  audioflinger: fix invalidateTracks() on offload thread

Change-Id: Ica11f6f42cdfbadc63ffd665410f483da0b1b2da