Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1655628

Description of problem:
Performance testing shows that there's most likely something done inefficiently in the Registered hosts report. I've tested on a Satellite with 10 000 systems.

When running a report without filters, it takes 8 minutes (there are no performance requirements specified so this should be fine). However, when running with a host filter such that it limits hosts to only 500 of these 10 000, the report generation consistently fails with ISE after 30 minutes.

Tested on a RHEL7 machine with Intel Xeon, 4 sockets, 32 cores, hyperthreading, 2.7 Ghz, 128 GB RAM

Version-Release number of selected component (if applicable):
6.5 snap 5

How reproducible:
Deterministic on one machine but may be influenced by the machine's performance.

Steps to Reproduce:
1. Have a Satellite with 10 000 systems, 500 of them with some easily filterable name
2. Monitor -> Report Templates -> Registered Hosts -> Generate
3. Fill in a filter such that it selects 500 systems
4. Submit

Actual results:
ISE after 30 minutes

Expected results:
Report generated. I'd expect it to be faster than without the filter