Bugfix tests

- Fix typo in Overlap Error (Closes JIRA CBDEUCE-211)
- Fix upload block should return X-Block-Reference-Count and X-RefModified (Closes JIRA CBDEUCE-255)
- Fix bug in Block Collection on_post, error message specified PUT instead of POST
I'll try switching it back; but I had an issue with it somehow returning None IIRC