Bug 2908

Step hasn't been assigned resources, so the select_jobinfo struct
hasn't yet been populated. Calling select_g_step_finish will dereference
causing a segfault.

Bug 2922.

Allow "sacctmgr delete cluster" to show running jobs on multiple
clusters when attempting to delete clusters with running jobs.

By freeing "object" if there were already jobs found on other clusters
prevents _check_jobs_before_remove_assoc() from selecting jobs from the
cluster because "cluster_name" will be NULL.

Happens when there are running jobs on the cluster.

_process_running_jobs_result() only does something if there were results
returned.

If the user is now allowed to use the partition,
    then do not check that user's group access again for 5 seconds.
bug 2913

Improve partition AllowGroups caching. Update the table of UIDs permitted to
    use a partition based upon it's AllowGroups configuration parameter as new
    valid UIDs are found rather than looking up that user's group information
    for every job they submit, which can involve considerable overhead for
    some systems.
bug 2913

Minimize preempted jobs for configurations with multiple jobs per node.
  Previous logic would preeempt every job on node allocated to pending
  job.
bug 2906

Fix for core selection with job --gres-flags=enforce-binding option.
    Previous logic would in some cases allocate a job zero cores, resulting in
    slurmctld abort.
bug 2808

Add some indentation so that GRES topology-specific information
  logged is more readable.

A job allocation selecting nodes and no cores/CPUs could write
  off the end of arrays and corrupt memory. Now to figure out how
  the logic reached this point in the first place.
bug 2808

In commit b8190e5d many places that were mean to be pending step ids
were changed to be extern_step id.  The main problem was when we came up
with the idea of the extern step we reused -1 (INFINITE) for the id.  So
pending steps also appeared to be extern steps as well.  Hopefully this
fixes the situation.

Bug 2907

Start power save thread only after the partition information is read
  in order to avoid trying to interpret the SuspendExcParts configuration
  information before the partition information is available, which would
  result in a slurmctld abort.

Do not try to access part_list variable (partition list pointer)
  if not yet initialized. Return NULL pointer rather than aborting
  with NULL pointer.

bug 2900

Don't register newly found buffers that are less than OtherTimout
  old to avoid possible duplicates.

This hardens the code with respect to a race condtion if the
  slurmctld restarts and a burts buffer creation for a job is
  in progress. Eliminate the possibility of a duplicate job
  allocation record.

No change in functionality, just moved function call and added
  comment

delete_step_records which would delete the steps without the killing flag
set.

What this does is treats the extern step like a normal step on exit.  It
doesn't appear the original code is needed anymore and this simplifies
the code.

The select_cray change is relevant since the add is needed only when
killing the step as that is the only place _internal_step_complete isn't
used.