Avoid re-creating Nova home directory when not in usegitrepo mode

This is always bound to conflict with the packages, and we're
fine with having any home directory being created. The one
configured by the packages should be the correct one.

This also simplifies the code a little.
Merge pull request #282 from dirkmueller/ssh_cleanup

Avoid re-creating Nova home directory when not in usegitrepo mode