Make sackd deb package create /etc/default/sackd rather than slurm_ops

[NucciTheBoss]

The sackd package from Debian currently does not create its own /etc/default/sackd package during installation. This means that sackd will fail to start as $SACKD_OPTIONS is left undefined in the systemd service file.

We can get around this by just having slurm_ops create the environment file with the proper file mode permissions in the _AptManager(...)._apply_overrides() method, but this should be something that's ideally handled by the upstream package instead as all sackd's will need this environment file to ensure that $SACKD_OPTIONS is defined.

Related issue in the Debian Bug Tracker for sackd: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1087927

[dsloanm]

This is fixed as part of Debian Sid's release of slurm-wlm/24.11.0-1: https://packages.debian.org/sid/amd64/sackd/filelist so just a matter of time until the creation step can be removed from slurm_ops.