Fix brittle catalog test

The old test actually made an HTTP request to an external service.
The new test stubs (only) the subprocess call of hets with a catalog.
use and_return.
remove stub calling the original.
comment the use of any_args.
Merge pull request #1076 from ontohub/fix-catalog_test

Fix brittle catalog test
Merge branch 'staging' into 617-handle_file_deletion