CentOS 8 Stream has been EOLd and our mirror automatically replicated
the empty package repo state set by upstream. The end result is that no
jobs that rely on this platform are able to run successfully any longer.
In preparation for removing these images entirely from zuul+nodepool we
remove the nodesets. We also remove some sanity checks in base jobs that
were geared towards moving people from CentOS 8 to CentOS 8 Stream. At
this point that is all moot and we shouldn't need it any longer.
Note I didn't split the base job change into a test change and a
production update change because all we're doing is removing some tasks.
This seems safe as these tasks shouldn't side effect in functional jobs.
Change-Id: I36baa3079e818b6504afcc6fe3743d3ec7de99eb
9cdb099d1d