Fixed problem clearing validation error on checkboxes.

The IPA.checkboxes_widget has been modified such that it performs
validation when the checkboxes are clicked. This will also clear any
validation errors.

install/ui/widget.js

@@ -924,6 +924,7 @@ IPA.checkboxes_widget = function (spec) {
         var input = $('input[name="'+that.name+'"]', that.container);
         input.change(function() {
             that.set_dirty(that.test_dirty());
+            that.validate();
         });
 
         that.create_error_link(container);