cbdocloader no longer supports keys in subdirectories

When dealing with particularly large sample buckets it makes sense to stick documents into subfolders (e.g. bucket.zip/docs/1/key.json) to reduce the directory length (Makes it a lot more manageable), unfortunately it looks like a refactor of the JSON pump broke this functionality as the current directory must now be called docs for it to work, not just in the directory path:

https://github.com/couchbase/couchbase-cli/commit/c892c9241d1e6997fa30317af791d6fcde73aeaa#diff-fc317540f1498eee77c5ba02a4fd9834L125

This should be really straightforward to fix.