Checking for ES plugin readiness before trying to use it

If the ES plugin is not ready (i.e. in red state), we won't try to use it and end
up blocking the reply.

src/ui/index.js

@@ -71,12 +71,15 @@ export default async (kbnServer, server, config) => {
       basePath: config.get('server.basePath'),
       serverName: config.get('server.name'),
       uiSettings: {
-        defaults: await uiSettings.getDefaults(),
-        user: await uiSettings.getUserProvided()
+        defaults: await uiSettings.getDefaults()
       },
       vars: defaults(app.getInjectedVars() || {}, uiExports.defaultInjectedVars),
     };
 
+    if (server.plugins.elasticsearch.status.state !== 'red') {
+      payload.uiSettings.user = await uiSettings.getUserProvided();
+    }
+
     return this.view(app.templateName, {
       app: app,
       loadingGif: loadingGif,