ImageReader: skip callback when image reader is being closed
ImageReader: skip callback when image reader is being closed

The application could acquire images in onImageAvailable callback when
the ImageReader is being closed. We need some protection here to avoid
application crash.

Change-Id: Ie5be8450048c0cfd78e5a7e27befe4de425d79f3

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base