userWidget: Fix avatar size

userWidget: Fix avatar size

The texture cache now returns an actor with an appropriate ClutterContent
rather than a ClutterTexture. That actor uses the CONTENT_SIZE request
mode, which means that it will unconditionally request the preferred size
of the content. That is, setting an explicit size no longer has an effect.

Fix this by making sure the image is already loaded with the desired
dimensions.

https://gitlab.gnome.org/GNOME/gnome-shell/issues/1024