tests: fail while running with ubuntu-20.04 on GA

[audrium]

Tests are not passing with ubuntu-20.04 because of directory hash mismatch (calculate_hash_of_dir used to calculate it). Error can be found here. With ubuntu-18.04 it works fine.

Originally posted by @audrium in https://github.com/reanahub/reana-commons/issues/237#issuecomment-729632233

Since it wasn't happening before, can you reproduce it locally? I would have guessed it would be somehow related to https://github.com/reanahub/reana-workflow-controller/commit/470171808bdb21e7917671c54fe2e0331f1ee67a, but it isn't because if the directory doesn't exist it would return -1 not a different hash. Some very wild guesses:

• Could something be wrong with the workspace, e.g. it already existed and had something else inside? (see possibility)
• Could it be that md5 behaves differently in this platform? see here (I don't think so since this was passing in the past.

Originally posted by @diegodelemos in https://github.com/reanahub/reana-commons/issues/237#issuecomment-729711113

[mvidalgarcia]

Fixed by https://github.com/reanahub/reana-commons/commit/24fd7662feb639a5a54140bd119e96775bf981c9