Cache results for major performance improvement.
bug 636

If a job request explicitly requests a GRES count of zero and that
is not the last GRES in the slurm internal data structures, the job
request will be rejected.
bug 633

Conflicts:
	src/plugins/switch/nrt/nrt.c

Perhaps should also look into doing this for nodeinfo and libstate

this would cause pmd's to hang.

This prevented jobs from sharing nodes

code.

remove typo

In test15.17, an salloc spawns an sbatch within that same job
allocation then exits. This results in a race condition which
can cause the terminate job RPC from slurmctld to slurmd to
briefly hang and mark the node non-responsive, causing later
tests that may need the node to fail (timeout waiting for
job allocation). A sleep is added to the salloc here to give
the batch job a chance to begin and clean up the job allocation
quickly.

This commit makes the QOS/Assocation tests a bit more thorough.
It also makes some minor format changes.