for https://github.com/fleetdm/fleet/issues/19020
- Fixes the rollback logic to get the right script for the software
being installed
- Fixes the messages displayed in the install results
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
<!-- Note that API documentation changes are now addressed by the
product design team. -->
- [x] Added/updated tests
- [x] Manual QA for all new/changed functionality