Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1929398

Description of problem:
When creating a nested hostgroup on the Satellite 6.8.2 web UI and inheriting the architecture and operating system from the parent hostgroup, if I select a different Operating System than the inherited one then no installation media will ever be available again.

This affects Satellite 6.7.5 as well, possibly earlier versions as well.

Version-Release number of selected component (if applicable):
satellite-6.8.2-1.el7sat.noarch
foreman-2.1.2.23-1.el7sat.noarch

and also

satellite-6.7.5-1.el7sat.noarch
foreman-1.24.1.32-1.el7sat.noarch

How reproducible:
100% of attempts.

Steps to Reproduce:
1. Create a host group named Parent that sets Lifecycle Env, Content View, Content Source, Architecture, Operating System, Installation Media.

2. Create a new host group named Child nested under Parent. On the Child host group, on the Operating System tab it will show:
Architecture: inherit parent (x86_64)
Operating system: inherit parent (RHEL Server 7.9)
Media Selection: Synced Content (I have the appropriate kickstart repo synced)
Installation Media: Red_Hat_Enterprise...Kickstart...7_9

3. Click the Operating system drop-down list and select something else, e.g. RHEL 7.8 or RHEL 8.3 (both of which are synced to Satellite as well.)

Actual results:
Media Selection will immediately set to All Media despite the appropriate kickstart repo (for RHEL 7.8 or RHEL 8.3 in this example) being synced correctly.
Media will show No options available for selected Operating System.
If I go to the drop-down list again and try to select 'Inherit parent RHEL Server 7.9)' like it was at first, still no media will show up and Media Selection will stay set to All Media instead of Synced Content.
The only way to select an OS other than the inherited one is to do away with all inheritance under the Operating System tab i.e. hard select Architecture=x86_64, Operating system=RHEL Server <whatever>, Media Selection=Synced Content, then Synced Content=Red_Hat_...Kickstart...7_8.

Expected results:
Any individual item in the Operating System tab should be overridable without affecting other inherited attributes. E.g. one should be able to inherit x86_64 as the architecture and still override the Operating System to a different RHEL version (major or minor).

Additional info:
N/A