Use error messages to be consistent, and avoid checking for a returned
value when dbus-glib function to fetch it returned false, as it's
implicit that we had a failure.
Otherwise if didn't fail we are sure that we got the requested value.
fprintd supports "any" finger parameter for the VerifyStart call, and it's
up to the daemon to pick the first known if the device doesn't support
identification.
So remove the check to verify utility and add a test to verify this is
respected.
These utilities are generally useful beyond only testing purproses. And,
since it is desirable to have automated tests inside the tests
subdirecty, it makes sense to move them elsewhere.
