We do not need gerrit-git-prep anymore, zuul-git-prep works on all our
slaves and has the advantage of using zuul-cloner so that the local
cache is used and Depends-On works.
Remove gerrit-git-prep and use zuul-git-prep instead everywhere.
Change-Id: I2f106af58f78fceaf3c497fe43e6f5a002695645
Adding training labs post jobs to publish tar/zip to
tarball.openstack.org. This should allow training-labs team to
automatically publish tarballs/zip files for the end-users of this
project and provide direct links from docs.openstack.org/training-labs
landing page.
Change-Id: I5dee9c7188b8b0cfd1bad31f320cc787eae5dcfa