136 - fixes for all_docs tests against clustered CouchDB / Cloudant

Running the current test suite against Cloudant, I came across the following issues in all_docs. This PR addresses some incorrect assumptions in the tests which also hold for clustered CouchDB. I didn't find anything which required a change to PouchDB logic - just the tests.
^ for this test, can we `sort()` and then keep the same assertion? It seems that, at least, we ca be sure that all four docs are there.