The boolean is just used to emit a warning for unexpected state
transitions. It is sufficient to pass it to the deactivate function
directly for that purpose.
The earlier image device code tried to hide deactivation from the
surrounding library. However, this does not make any sense anymore with
the early reporting feature present.
This changes the operation to complete only once the device is
deactivated. Also changed that in most cases (except for cancellation)
we wait for the finger to be removed before deactivating the device.
In order to be able to test the private device code (used by drivers) we
need to have that split a part in a different .c file so that we can compile
it alone and link with it both the shared library and the test executables.
Redefine fp_image_device_get_instance_private for private usage, not to move
the private struct as part of FpDevice.
