pk-client: Fix pkmon gtask warning caused by PkClient refcount issue

Fixes 'GTask finalized without ever returning (using
g_task_return_*())' warning message while running `pkmon` and gives
the proper output.

This was caused because `PkClientState` was finalized incorrectly,
causing the state's gtask object to be finalized causing the warning.

Fixes: PackageKit#709

lib/packagekit-glib2/pk-client.c

@@ -194,6 +194,8 @@ pk_client_state_unset_proxy (PkClientState *state)
 						      state);
 		g_clear_object (&state->proxy);
 	}
+
+	g_object_unref (state);
 }
 
 static void
@@ -1657,6 +1659,8 @@ pk_client_proxy_connect (PkClientState *state)
 	guint i;
 	g_auto(GStrv) props = NULL;
 
+	g_object_ref (state);
+
 	/* coldplug properties */
 	props = g_dbus_proxy_get_cached_property_names (state->proxy);
 	for (i = 0; props != NULL && props[i] != NULL; i++) {