Simplify /podmin redirect

Some podmins were confuse how they can disable this redirect and I think
the rule with two users can actually be a little confusing. I think the
main goal of this page to give the podmin a little start and I think
after they configured everything, the pod works and they found the link
to the wiki to make themself an admin, it is OK to remove the redirect.

Also it's bad for single-user pods where this page always stays active,
even if they are an admin, but have only one user. It's more useful for
single-user pods to have the login on the home page.

closes #7783