Fix loopback test (#773)

Author: fhinkel

appengine/loopback/package.json

@@ -27,6 +27,7 @@
     "loopback": "3.18.2"
   },
   "devDependencies": {
+    "@google-cloud/nodejs-repo-tools": "^2.3.5",
     "eslint": "4.18.2",
     "eslint-config-loopback": "10.0.0",
     "nsp": "3.2.1"