Description of problem:

Using "select all" on a Host's errata page and applying errata via REX causes all errata on the system to be added to the call to dnf.

How reproducible:

100%

Is this issue a regression from an earlier version:

Likely, yes, and 6.15.0.

Steps to Reproduce:

1. Sync a repository with errata

2. Register a host with a few installable errata

3. Use 'select all' on the host errata page and apply said errata via REX

Actual behavior:
All errata in the system get applied to the resulting dnf call

Expected behavior:

Only the selected errata get applied to the host

Business Impact / Additional info:

The use of "check_installable_for_host: false" in the related REX job template was originally to work around the case where a user tries to install RPMs or apply errata to a host that has a stale package profile. We hoped that DNF could be the source of truth for if the errata are installable or not. However,  since 'select all' uses an empty search query string, it seems we do need to let Katello scope the installed errata to what is applicable to the host (or the 'select all' logic needs to actually send all errata IDs to the API).