CameraModule: fix getCameraInfo()

Remove mCameraCharacteristicsMap.

CameraModule kept a CameraMetadata in mCameraCharacteristicsMap
and kept its camera_metadata in mCameraInfoMap. When CameraMetadata
gets moved in mCameraCharacteristicsMap, it may clone a new
camera_metadata and free the old one. So the original
camera_metadata stored in mCameraCharacteristicsMap becomes invalid.

Bug: 22171288
Change-Id: Ia8e99fe42989946bc952ad23abb296aeac60da83