backends: Plug leaks

The DRM properties container must be destroyed with
drmModeFreeObjectProperties, and the connectors must be freed on every
caller. Also make it sure that gbm_device structs are destroyed with the
MetaRendererNativeGpuData that owns them.

https://bugzilla.gnome.org/show_bug.cgi?id=789984

src/backends/native/meta-renderer-native.c

@@ -243,6 +243,7 @@ meta_renderer_native_gpu_data_free (MetaRendererNativeGpuData *renderer_gpu_data
   if (renderer_gpu_data->egl_display != EGL_NO_DISPLAY)
     meta_egl_terminate (egl, renderer_gpu_data->egl_display, NULL);
 
+  g_clear_pointer (&renderer_gpu_data->gbm.device, gbm_device_destroy);
   g_free (renderer_gpu_data);
 }