Also only keep around realmd while we're actually using it, allow it to quit if no other clients are active. https://bugzilla.gnome.org/show_bug.cgi?id=698200
Different networks have different user identifers. This can be confusing to the user, so to make it clearer, we try to provide a hint. https://bugzilla.gnome.org/show_bug.cgi?id=681975