[PLT-7180] Fix delete/edit not showing on DotMenu at parent post of RHS (#7214)

* fix delete/edit not showing on DotMenu at parent post of RHS

* remove unnecessary shouldComponentUpdate

webapp/components/dot_menu/dot_menu.jsx

@@ -71,6 +71,15 @@ export default class DotMenu extends Component {
         $('#' + this.props.idPrefix + '_dropdown' + this.props.post.id).on('hidden.bs.dropdown', () => this.props.handleDropdownOpened(false));
     }
 
+    componentWillReceiveProps(nextProps) {
+        if (nextProps.post !== this.props.post) {
+            this.state = {
+                canDelete: PostUtils.canDeletePost(nextProps.post),
+                canEdit: PostUtils.canEditPost(nextProps.post, this.editDisableAction)
+            };
+        }
+    }
+
     componentWillUnmount() {
         this.editDisableAction.cancel();
     }