Machines should not wipe workspace after runs if they are taken offline during the run

[mmitche]

To avoid disk space issues, we wipe the workspace before and after runs. This is fine, except when someone needs to investigate something. In that case, the workspace is gone before there is a chance to look at it.

Although I do not know whether it's easy to achieve, it would be nice to have the workspace not be wiped if the machine is offline at the end of the build. This would allow for easy investigation.