Fix RL8.6 and EPEL repo changes

[sjpb]

• Remove releasever pinning (pinning to 8.6 no longer works as packages have been moved to Vault)
• Bumps the "fat" image for CI appropriately (Fix RL8.6 and EPEL repo changes slurm_image_builder#13)
• Adds an older apptainer package from github release, to workaround Can not install ohpc-gnu12-runtimes on Rocky 8 openhpc/ohpc#1644 (EPEL package changes break dependencies for ohpc-base-compute package).

[sjpb]

Checks were failing as volumes were /dev/sd*. Fixed by running:

openstack image set \
--property hw_rng_model=virtio \
--property hw_scsi_model=virtio-scsi \
--property hw_disk_bus=scsi \
--property hw_vif_model=virtio \
openhpc-230104-1319.qcow2

[sjpb]

Closed and reopened to force CI to run

[m-bull]

While this is a fine workaround for now, we should probably put some time into working out how to build from Rocky GenericCloud images again when we have the capacity.

[sjpb]

We can built from GenericCloud 8.6 images, that is what the "fat" image openhpc-221118-1422.qcow2 is based on (the link to the fat image PR is the other change in the TF). We just can't build from 8.7 images cause they appear to be broken.