AImage: don't allow ~AImageReader to run before AImages are deleted.

We can never be sure whether ~AImageReader() has run to completion or
not in AImage::close(). So we move clean up to another AImageReader
method and make sure that's called when in AImageReader_delete. AImage
now contains an sp<> to AImageReader so we can be sure that its members
wouldn't have been destroyed by ~AImageReader and we can check whether
AImageReader_delete has been called on it.

This also prevents us from deadlocking since AImage_delete could also cause
~AImageReader to run with AImageReader::mLock held in AImage::close().

Bug: 137571625
Bug: 137694217

Test: enroll; auth
Test: cts native AImageReader, camera, graphics tests

Change-Id: If5803cb6fcb6f4800032069872daaeac1cd36ed2
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>