hwc: Do not wait for async task to finish.

- Remove wait for async task to finish.
  Task can finish only when async function
  call has finished. However, PostRefresh
  completion depends on HWC mutex to be
  unlocked.

Change-Id: If7ffae33179d909df46dbbfa40810ad8068924bb
CRs-Fixed: 2037550
2 files changed