This has nothing to do with the Enterprise Sites issue. I followed and remediated my environment to address that issue. This is all about ArcGIS Server. As I said -
"I then looked for the ArcGIS Server Windows service and it is not there."
So: after successfully running the Setup.exe for ArcGIS Server, successfully authorizing the software, the post-upgrade launches in the default browser. BUT no post-upgrade steps could happen because the ArcGIS Server window service is not there. It is not present as a windows service.
When I downloaded the software from MyEsri, I ran checksum on all of the packages and everyone of them came back with a matching string. In other words, no files, cabs, dlls etc etc were missing from the software.
I then performed an uninstall and re-install of ArcGIS Server. Upon a re-install, the ArcGIS Server Windows service is present. It is there. However, at that time the only choices are to create a new site or join an existing ArcGIS Server site, because a re-install of the software is just that, the existing ArcGIS Server site no longer sees the machine as registered with the site. You can't join an existing site because (for us) the other machine in the site cluster is still at 11.1.
Creating a new site is not an option, not without completely re-creating our entire deployment.
We do use a domain account to run all enterprise components (portal for arcgis, arcgis server, data store).
The interesting thing is that the same domain account successfully upgraded portal to 11.2, and re-created the Portal for ArcGIS windows service. My guess is something in our Carbon Black may be seeing the upgrade or an upgrade file as malware. Who knows.
So for the first time in 17 years of updating either ArcGIS for Server and then ArcEnterprise, I have had to roll back my install to 11.1.
@JonEmch