Camera: Quit extension handler thread during release

The extension framework logic assumes that there will be
no further handler loop processing after the release
method quits the corresponding thread.
The current approach does allow pending messages to be
handled which depending on timing can result in data
races.
To avoid potential data races ensure that the handler
thread quits regardless of any queued messages.
Additionally synchronize access to 'mImageListenerMap'
in 'CameraOutputImageCallback'.

Bug: 278160240
Bug: 285886910
Test: Camera CTS
Change-Id: I3a78fa566cfe72dbfa1bc5721854823243e03f23