paint-node: Make texture template pipeline clamp to edge

It's safer, and consistent with the rest of Clutter, to make sure that
the template pipeline we use for ClutterTextureNode has its wrap mode
set to clamp-to-edge.

clutter/clutter-paint-nodes.c

@@ -79,6 +79,8 @@ _clutter_paint_node_init_types (void)
   cogl_pipeline_set_layer_null_texture (default_texture_pipeline, 0,
                                         COGL_TEXTURE_TYPE_2D);
   cogl_pipeline_set_color (default_texture_pipeline, &cogl_color);
+  cogl_pipeline_set_layer_wrap_mode (default_texture_pipeline, 0,
+                                     COGL_PIPELINE_WRAP_MODE_CLAMP_TO_EDGE);
 }
 
 /*