We were not testing the image device error reporting functions yet
inside libfprint (fprintd already had such tests). Add tests to make
sure we catch errors earlier.
It is a good idea to report match results early, to e.g. log in a user
immediately even if more device interaction is needed. Add new _full
variants for the verify/identify functions, with a corresponding
callback. Also move driver result reporting into new
fpi_device_{identify,verify}_report functions and remove the reporting
from the fpi_device_{identify,verify}_complete calls.
Basic updates to code is done in places. Only the upekts driver is
actually modified from a behaviour point of view. The image driver code
should be restructured quite a bit to split the reporting and only
report completion after device deactivation. This should simplifiy the
code quite a bit again.
This also changes the code to keep the connection open and adds
automatic mainloop iteration to ensure the driver processes the request.
This is important so we will not deadlock when we send multiple
requests.
