tests/fprintd: Use addCleanup to always terminate daemons

Ensure that the daemons are always terminated after each test, even on
failure, so that we don't have to do hacks such as always trying to stop
them

tests/fprintd.py

@@ -191,6 +191,7 @@ class FPrintdTest(dbusmock.DBusTestCase):
                                        env=env,
                                        stdout=None,
                                        stderr=subprocess.STDOUT)
+        self.addCleanup(self.daemon_stop)
 
         timeout_count = timeout * 10
         timeout_sleep = 0.1
@@ -245,6 +246,7 @@ class FPrintdTest(dbusmock.DBusTestCase):
     def polkitd_start(self):
         self._polkitd, self._polkitd_obj = self.spawn_server_template(
             'polkitd', {}, stdout=DEVNULL)
+        self.addCleanup(self.polkitd_stop)
 
     def polkitd_stop(self):
         if self._polkitd is None:
@@ -288,8 +290,6 @@ class FPrintdVirtualDeviceTest(FPrintdTest):
         self.daemon_start()
 
         if self.device is None:
-            self.daemon_stop()
-            self.polkitd_stop()
             self.skipTest("Need virtual_image device to run the test")
 
         self._polkitd_obj.SetAllowed(['net.reactivated.fprint.device.setusername',
@@ -326,9 +326,6 @@ class FPrintdVirtualDeviceTest(FPrintdTest):
     def tearDown(self):
         self.device.disconnect(self.g_signal_id)
 
-        self.daemon_stop()
-        self.polkitd_stop()
-
         del self.manager
         del self.device