Bugfix. Detach the element before positioning it again.

Otherwise the index of the element relative to which we place it changes
depending on whether the element being positioned is placed before or after it.

converse.js

@@ -3275,6 +3275,7 @@
                  */
                 var view = this.get(contact.get('id'));
                 var index = this.model.contacts.indexOf(contact);
+                view.$el.detach();
                 if (index === 0) {
                     this.$el.after(view.$el);
                 } else if (index == (this.model.contacts.length-1)) {