Zoho has started returning the results from Range: requests with a 200
response code rather than the technically correct 206 error code.
Before this change this triggered workaround code to deal with Zoho
not obeying Range: requests properly.
This fix tests the returned header for a Content-Range: header and if
it exists assumes it is a valid reply to the Range: request despite
the status being 200.
This problem was spotted by the integration tests.
Nick Craig-Wood
4f8dab8bce