camera2 vndk: Don't try to retrieve ACameraDevice in CallbackHandler.

Its possible that the device is closing, however, it hasn't stopped its
looper yet. In that case, if we receive a callback, we'll receive a null ACameraDevice. Cache the
camera id during CallbackHandler's construction instead, like the ndk does.

Bug: 130910407

Test: AImageReaderVendorTest

Change-Id: Ia7cd40ff1ce4fe52abb5528c68e3557523a5367d
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>