Rename nexus-2 back to nexus and change other scripts accordingly

[robe]

As mentioned in #2932 I ran into issues after fiddling with the security setting of nexus, so I had created a new version and called it nexus-2.

I have now successfully deleted the old nexus, so can put nexus-2 back to original name of nexus. Instead of a rename, I'm planning to do a copy as I think that is a bit faster and will result in no downtime.

Once done, I will switch the backup scripts for osgeo4, back to copying nexus and also the webconfigs for docker*.osgeo.org and repo.osgeo.org back to nexus.