Test net.i2p.util.ConvertToHash

This MR tests net.i2p.util.ConvertToHash.getHash() and raises its coverage to 100%.

It's based on !12 (merged) in order to have gitlab.com run CI tests, but once that MR is merged, this one should not include the .gitlab-ci.yml diff.

You can see the CI results on gitlab

TODO

• Figure out how to mock Destination d = I2PAppContext.getGlobalContext().namingService().lookup(peer);