Support rewriting the image name

[natefoo]

So that I can drop this hack

I am not sure, I think I tried an unstructured path rewrite for this and it didn't work, but I can check again, just didn't want to lose track of this issue.

[mvdbeek]

Since the container resolution happens in Galaxy I think that would currently be the place where you would set this. I suppose a per destination container config would make sense. This is possible for the docker container resolver and would be relatively easy to set up. It would be nice though if pulsar could do the container resolution, container volume mounting and command line building, since then admins can set up a pulsar endpoint without having to adjust the Galaxy config for the specific settings of the pulsar destination.

[natefoo]

I think maybe a proper integration of cvmfsexec might be nice as well, but maybe it's overkill.