Rocky 8 image creation is missing slurm-slurmd package

[mulderij]

Rocky 8 image creation (and possible more) using playbook compute-default.yml (0a84779) is missing package slurm-slurmd when not installing OpenHPC. The installation uses {{ slurm_packages }} from site/roles/trinity/slurm/defaults/main.yml c8987aa.

(Also a compute image shouldn't need slurmctld and slurmdbd)