[glx-texture-pixmap] Unref a cogl texture handle.

According to clutter_texture_set_cogl_texture you should unref the handle as
the texture takes its own.

Signed-off-by: Robert Bragg <robert@linux.intel.com>

clutter/glx/clutter-glx-texture-pixmap.c

@@ -377,6 +377,7 @@ create_cogl_texture (ClutterTexture *texture,
       priv->using_rectangle = using_rectangle;
 
       clutter_texture_set_cogl_texture (texture, handle);
+      cogl_texture_unref(handle);
 
       return TRUE;
     }