tests/dbus-runner: Make sure to tear-down even on test failure

When a test failed, an exception would be raised. This meant that the
mocked service would stay alive, and the test case being run eventually
failing due to a timeout, not the failure itself.

Fix this by catching the exception during the test, ensuring that we
tear down properly, then re-raise the same exception again after having
teared down.

This avoids the dead lock, while still printing the appropriate error
message.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2008>

src/tests/meta-dbus-runner.py

@@ -122,5 +122,7 @@ if __name__ == '__main__':
     MutterDBusTestCase.setUpClass()
     test_case = MutterDBusTestCase()
     test_case.assertGreater(len(sys.argv), 1)
+    try:
         test_case.wrap_call(sys.argv[1:])
+    finally:
         MutterDBusTestCase.tearDownClass()