save initial pulp3 repo version creation at creation time instead of metadata generate
As it would be much simpler
Fixes #28461 - simplify initial version_href saving
previously we had to create a new version for a newly created
pulp3 repository manually. But starting with rc8, one is created
for us automatically. This changes repo creation to save
the version_href at creation time, instead of waiting until
metadata generate is called.