slurmdb_pack_assoc_usage() will assert with a NULL usage ptr.

7d9a75df uncovered that slurmdb_pack_assoc_usage() expects a usage
ptr.

Used by new node features development

Bug 4469

This is a continuation to c539d346 where this should had been removed
in the first place.

Bug 4127

bug 4539

When --mail-type option isn't requested with ARRAY_TASKS, we need somehow
to summarize the different states each task finished in the array. We've
added a new ARRAY_TASK_REQUEUED flag to the array_flags to indicate that
at least one task was requeued. Also the logic now detects if at least
one task failed and/or if otherwise all finished successfully.

The patch also removes the RunTime from the the e-mail when summarizing
whole array, since it doesn't make sense to specify just the RunTime
of one of the tasks for this case.

Patch also fixes when ARRAY_TASKS is specified, previously the mail
notification for the master job task record included a range of
ExitCodes for all the tasks. Since this option is not for summarizing,
the patch makes it so only the range is shown when the option isn't
specified.

Bug 4539.

Scheduling fix for changing node features without any NodeFeatures plugins.
Bug 4577

695d33b8 removed the REQUEST_SIGNAL_TASK_GLOBAL case statement which was
the only case statement that didn't set an use the rc = SLURM_SUCCESS.

Bug 4329
Bug 4312

Bug 4448

Avoid setting node in COMPLETING state indefinitely if the job initiating
the node reboot is cancelled while the reboot in in progress. Bug
introduced in commit 7d246784

Bug 4536

Bug 4448

# Conflicts:
#	NEWS

Updated also some link references as agreed by e-mail with R. Castain.

Continuation of bbfd1890.

This should have been part of commit 75f0789d
bug 4531

bug 4575

Update slurm.spec and slurm.spec-legacy as well

Add job state flag of "SIGNALLING" to avoid race condition with multiple
    SIGSTOP/SIGCONT signals for the same job being active at the same time.
bug 4531

Logic was backwards before.

Bug 4459.

These tests were failing on a single node cluster