support job requests that exclude specific nodes/resources

[garlick]

The point of contact for SNL's SPARTA code is Stan Moore:

On Trinity, his code uses the following srun options: --cpu_bind=core (or threads), -u, --exclude, -N, --ntasks-per-node. -u is used as it is helpful for debugging.

Originally posted by @dongahn in #2150 (comment)

[stale]

This issue has been automatically marked as stale because it has not had activity for 365 days. It will be closed if no further activity occurs within 14 days. Thank you for your contributions.

[grondo]

FYI - we do support exclusion of individual nodes now with sched-simple via --requires ^hostname, though long term we shall propose a hostlist specific constraint operator. Closing this one for now though.