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

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.

functions.

Before it was showing it as TBD since pending steps and the extern step
have the same stepid.

What this does is set the state earlier to match a normal set.

Remove the unneeded _send_pending_exit_msgs.  There is only one task and
we have the message for it, so don't worry about that one.

Most important, wait for the other slurmstepd's to send their message,
otherwise they could be lost on the other end.

Fix gang scheduling and license release logic if single node job killed on
    bad node. Notifying gang and releasing licences is normally done when
    the epilog completion happens, but if the node(s) assigned to a job are
    all down, that does not happen. This results in the licenses being
    reserved indefinitely and the gang scheduler being left with a bad
    (old) job pointer that can result in various failure modes
bug 2867

Add hotels. Other minor changes.

anyway to attempt to log the backtraces of the potential
unkillable processes.

667f1105.

We have decided to go back to the way 15.08 called NHC instead of calling
it first before sending a SIGKILL to the steps tasks.  With this patch we
only start the NHC early when we have to resend the SIGKILL for unkillable
processes.  This will hopefully get us the backtrace of the unkillable
processes which was the reason we did it this way in the first place :).

processes.

Bug 2892.

Bug 2874

We will most likely redo this logic (as it appears to be duplicated) in
a following patch.

Don't generate an error when a batch job is submitted that must wait
  for stage-in before starting.

Bug 2886

Conflicts:
	src/sstat/options.c

Was incorrectly translating request to job.extern if part of a
comma-separate list.

Bug 2890.

(regression in 16.05.2).

related commit 5d3e5e1e

Bug 2612 and 2886