Update webhook posts to never show in collapsed view

webapp/components/post.jsx

@@ -188,6 +188,8 @@ export default class Post extends React.Component {
             if (post.props && post.props.from_webhook && global.window.mm_config.EnablePostIconOverride === 'true') {
                 if (post.props.override_icon_url) {
                     src = post.props.override_icon_url;
+                } else {
+                    src = Constants.DEFAULT_WEBHOOK_LOGO;
                 }
             } else if (Utils.isSystemMessage(post)) {
                 src = Constants.SYSTEM_MESSAGE_PROFILE_IMAGE;