tests/fprintd: Ensure that the daemon doesn't crash or abort

An application terminating because of a signal like SIGSEGV, SIGABRT and
friends, will exit with a signal number that is 128 + $SIGNAL_NUMBER, so
let's ensure that the daemon has not been terminated because of a such error

This makes even more sense with address sanitizer builds, as the daemon
would exit with abort.

tests/fprintd.py

@@ -241,7 +241,7 @@ class FPrintdTest(dbusmock.DBusTestCase):
                 self.daemon.terminate()
             except OSError:
                 pass
-            self.daemon.wait(timeout=2)
+            self.assertLess(self.daemon.wait(timeout=2), 128)
 
         self.daemon = None