Camera: Delay pingCameraServiceProxy to end of onFirstRef

The cameraservice is only registered to service manager after onFirstRef
is returned. To reduce the probability of getBinderService() call
returning null, move pingCameraServiceProxy to end of onFirstRef().

Also add debug messages in onFirstRef and main() for better diagnoses.

Test: Camera CTS
Bug: 140414594
Change-Id: I52defd1c138ade57ebc5181c42aff30921fbeaeb