tests: Derive configuration when stage views is disabled

In order to test deriving the logical state from the underlying
configuration, as is always done on X11, make the test backend derive
the state when stage views are disabled.

https://bugzilla.gnome.org/show_bug.cgi?id=777732

src/tests/monitor-store-unit-tests.c

@@ -510,6 +510,12 @@ meta_test_monitor_store_scale (void)
       return;
     }
 
+  if (!meta_is_stage_views_enabled ())
+    {
+      g_test_skip ("Not using stage views");
+      return;
+    }
+
   set_custom_monitor_config ("scale.xml");
 
   check_monitor_configurations (&expect);