tests: Add MetaMonitorConfigStore tests

Add tests that check that a XML configuration file results in correct
MetaMonitorsConfig objects.

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

src/tests/monitor-unit-tests.c

@@ -589,9 +589,9 @@ create_monitor_test_setup (MonitorTestCase *test_case)
                                                     ++n_laptop_panels)
                                  : g_strdup_printf ("DP-%d",
                                                     ++n_normal_panels)),
-        .vendor = g_strdup ("MetaProducts Inc."),
-        .product = g_strdup ("unknown"),
-        .serial = g_strdup ("0xC0FFEE"),
+        .vendor = g_strdup ("MetaProduct's Inc."),
+        .product = g_strdup ("MetaMonitor"),
+        .serial = g_strdup ("0x123456"),
         .suggested_x = -1,
         .suggested_y = -1,
         .hotplug_mode_update = TRUE, /* Results in config being ignored */