luci-mod-network: properly reflect config state in sysfs tristates

When a boolean sysfs option is forcibly set to `0` or `1` in uci, then make
sure to properly reflect that choice state when rendering the widget.

Right now the dropdown incorrectly reverted to "automatic" after saving but
not applying the changes.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-mod-network/htdocs/luci-static/resources/tools/network.js

@@ -198,7 +198,7 @@ var cbiFlagTristate = form.ListValue.extend({
 			this.vallist[0] = sysdef ? _('automatic (enabled)') : _('automatic (disabled)');
 		}
 
-		return this.super('renderWidget', [section_id, option_index, cfgvalue]);
+		return this.super('renderWidget', [section_id, option_index, cfgvalue ? cfgvalue + '!' : null]);
 	}
 });