DO NOT MERGE: Minimal fix for takePicture/previewCallback deadlock

- Caused by already held lock in camera service

- Introduce one more lock, mICameraLock, to control access to camera
  client through ICamera binder interface.

- mLock is released before calling HAL takePicture, allowing HAL
  callbacks to access camera client during takePicture processing.

Bug: 5804701
Change-Id: Ibcef4857a2c844c964afefa70f9cdccdd0a55fd0