Coverity CID 190390, 190393, 190397

Fix for Coverity CID 190461

Add small note to documentation to clarify how to set different SlurmUser for
slurmdbd and ctld.

Bug 6306

This fleshes out logic so scontrol can be used to update a node's GRES.

Previous logic was failing to report errors in node's GRES update
requests.

No change in logic, improve some comments and logging

This is only used to define the slurmctld_comm_addr symbol in allocate.h.
Variable definitions do not belong in headers. Rather than relocate the
struct declaration, replace the struct which only holds a single port number
with a static variable serving the same purpose in allocate.c, and the
extern in this same location so srun.c can find it as well.

Replaces the Linux SO_PEERCRED calls.

This improves handling of job requests for GRES with zero counts.
Previously if gres/foo had a count of zero, then "srun --gres=foo ..."
would generate an invalid TRES error, while "srun --gres=foo:1 ..."
would just pend. Now they both pend.

Regression introduced in ccafaf7b.

Replace the (was always set to true) check_current_dir argument to
search_path() with check_cwd_last boolean to indicate if cwd should be
evaluated first (needed by sbatch) or last (salloc/srun).

Bug 6271.

Without this patch the Gres count might be reported as "NAME:0G" rather
than just "NAME:0".

No functional change intended.

Kill running/pending job is allocated GRES and that GRES has a "File"
    configuration, and the GRES count changes.
Also generally better handle changes in GRES count (avoid some bugs
    in GRES data structures).

(Name change presumably missed due to the typo.)

This properly sets up the node's GRES data structure for gres/mps
with CLOUD based nodes. This sets the counters appropriately for
nodes which are not up when the slurmctld restarts.

This fixes test39.18 to work with slurm logic corrected in
commit 992e393f

Coverity CID 190597

The logic is flawed with respect to gres/mps and cloud based nodes.

without this change GRES with large count values would
have those values silently changes (i.e. Count=4G changed
to a count of 0).

If we get an error on one record, try to keep loading others
to at least validity check them

The RPC change only happened in v19.05

without this change if gres/mps is configured in gres.conf without
files then gres.c logic will try to access the topo array, which
is NULL.

this keeps the gres data structures consistent in slurmctld when their
  count changes or is inconsistent with slurmd
also kill jobs allocated to gres with files if their count changes.

If a node's GRES state was recovered, this logic would see
the record and clear it's configured count resulting in
invalid node GRES information.

bug 6304

This is important for gres/mps, where the
bitmap size and GRES count will differ

bug 6304