Camera: Synchronize callback access to composite map

Access to the camera device client composite map is not
thread safe during device callbacks. To avoid possible
deadlocks, synchronize access to the map via separate
dedicated lock.
Additionally correct the composite graphic producer query
when switching to offline mode.

Bug: 212496312
Test: Camera CTS, partner testing
Change-Id: I25b24466fbcf88a85d1c28b874812ff5c102c250