CRAY - Switch to standard pid files on Cray systems.

Bug 4500

The pid files in slurm.conf and the systemd service files must match,
or systemd will time out looking for the wrong pid file. Currently,
the Cray slurm.conf template has different pid files for slurmctld and
slurmd than the service files.

There's no reason for us to use these nonstandard pid files, and it
will save us some headaches to switch over.