Update Mongodb client to 2.2.4 (#2329)

* chore(package): update mongodb to version 2.2.4

https://greenkeeper.io/

* fix for mongo 2.2.4

* Delete schema promise on error...

- Just because this way we can let the adapter an opportunity to yield a new error....
OR A SUCCESS

* Fixes test

* Restore fix

package.json

@@ -31,7 +31,7 @@
     "lru-cache": "4.0.1",
     "mailgun-js": "0.7.10",
     "mime": "1.3.4",
-    "mongodb": "2.1.18",
+    "mongodb": "2.2.4",
     "multer": "1.1.0",
     "parse": "1.9.0",
     "parse-server-fs-adapter": "1.0.0",