Bug 1798

If a job can only be started by preempting other jobs, the old logic
  could report the error:
  "cons_res: sync loop not progressing, holding job #"
  due to the usable CPUs and GRES needed by the pending job not
  matching. This change prevents the error message and job hold
  when job preemption logic is being used. The error message and
  job hold still take place for job scheduling outside of preemption,
  which will match CPUs and GRES at the beginning.
bug 1750

Under some conditions the select/cons_res plugin will hold a job,
  setting it's priority to zero and reason to HELD. The logic in
  slurmctld's main scheduling loop previously kept its priority
  at zero, but changed the reason from HELD to RESOURCES. This
  change leaves the proper job state as set by the select plugin.
This may be related to bug 1750

The backfill scheduler will periodically release locks for other
  actions. If a job is held during the time that locks were released,
  that job might still have been scheduled by the backfill scheduler
  (i.e. it failed to check for a job with a priority of zero).
could be a root cause for bug 1750

Previous logic could fail to update some tasks of a job array for
  some fields.
bug 1777

Add level to switch table information logged by select plugin

Old logic could purge a job record for a job that was in
  completing state (if there was also a lot of agent threads).
  This change prevents purging job records for completing jobs.

Fix to job array update logic that can result in a task ID of 4294967294.
To reproduce:
$ sbatch --exclusive -a 1,3,5 tmp
Submitted batch job 11825
$ scontrol update jobid=11825_[3,4,5] timelimit=3
$ squeue
             JOBID PARTITION     NAME     USER ST       TIME  NODES NODELIST(REASON)
           11825_3     debug      tmp    jette PD       0:00      1 (None)
           11825_4     debug      tmp    jette PD       0:00      1 (None)
           11825_5     debug      tmp    jette PD       0:00      1 (None)
             11825     debug      tmp    jette PD       0:00      1 (Resources)
A new job array entry was created for task ID 4 and the "master" job
array record now has a task ID of 4294967294.
The logic with the bug was using the wrong variable in a test.
bug 1790

Bug 1799

remove new capabilities added in comit ad9c2413
Leave the new logic only in version 15.08, which has related
performance improvements in the slurmctld agent code, see commit
53534f49

Correct "sdiag" backfill cycle time calculation if it yields locks. A
    microsecond value was being treated as a second value resulting in an
    overflow in the calcuation.
bug 1788

The slurmctld logic throttles some RPCs so that only one of them
can execute at a time in order to reduce contention for the job,
partition and node locks (only one of the effected RPCs can execute
at any time anyway and this lets other RPC types run). While an
RPC is stuck in the throttle function, do not count that thread
against the slurmctld thread limit.
but 1794

This patch moves the QOS update of an existing job to be before the
partition update.  This ensures a new QOS value is the value used when
doing validations against things like a partition's AllowQOS and DenyQOS.

Currently if a two partitions have AllowQOS that do not share any QOS,
the order of updates prevents a job from being moved from one partition
to another using something like the following:

scontrol update job=<jobID> partition=<new part> qos=<new qos>

Correct task layout with CR_Pack_Node option and more than 1 CPU per task.
Previous logic would place one task per CPU launch too few tasks.
bug 1781

Backfill scheduler now considers OverTimeLimit and KillWait configuration
parameters to estimate when running jobs will exit. Initially the job's
end time is estimated based upon it's time limit. After the time limit
is reached, the end time estimate is based upon the OverTimeLimit and
KillWait configuration parameters.
bug 1774

Backfill scheduler: The configured backfill_interval value (default 30
    seconds) is now interpretted as a maximum run time for the backfill
    scheduler. Once reached, the scheduler will build a new job queue and
    start over, even if not all jobs have been tested.
bub 1774

Bug 1745

This reverts commit 3f91f4b2.

and test21.* updated to use them.

Bug 1745

ESLURM_DB_CONNECTION when in error.