Return ok:true on _bulk_doc update

The tests are separated and are quite funky. The main
reason why I also submit them is to get some 
opinions and maybe a discussion  about 
integration-tests for `couchdb-chttpd` running.

- I could imagine something based on Erlang to test 
chttpd which has better quality than my code.

- Another solution would be something JS/node based,
I am more used to that and faster in writing JS, but it
may not apply to everyone

- Use a complete different language / solution to test

---

Return `ok: true` on a successful _bulk_doc update like in
CouchDB 1.6.

Example success message on 2.0:
```
[{"id":"Brocket","rev":"6-b6fa9e703c3eb92aa9c3a49cedf1e8c2"}]
```

Example error message on 2.0:
```
[{"id":"Blaggie-System","error":"conflict",
  "reason":"Document update conflict."}]
```

Finally closes COUCHDB-2462
Sorry, miss it. I believe that the failure is related to how you run the server.
AFAIK, the JS tests are don't test cluster interface and changing this will lead to fixing JS test suite too.