Test was failing sometimes due to varying Expect buffering

Now have one launch step per pack job component, so no duplicate
launch errors

Use it for setting output label when the output/error file name
  includes the "%N" format option (node name, e.g. "--output=out.%N").

Correct some logic so that pack_gorup and pack_grp_bits fields
  are properly set.

$ srun --pack-group=1,2 -l tmp
0: JOBID:43740 HOST:nid00002
0: JOBID:43741 HOST:nid00003
1: JOBID:43741 HOST:nid00003
1: JOBID:43740 HOST:nid00002
2: JOBID:43740 HOST:nid00002
2: JOBID:43741 HOST:nid00003
3: JOBID:43741 HOST:nid00003
srun: error: Task 0 reported exit for a second time.
srun: error: Task 1 reported exit for a second time.
srun: error: Task 2 reported exit for a second time.

srun now parsing for the "-pack-group" option first,
  then processes the environment variables for that pack group,
  then processes the remaining options for the pack group.
srun will still only spawn tasks for one pack group at a time,
  but will at least handled forwarded options from the job
  allocation phase (i.e. sbatch or salloc).

Change (almost) all references to use pointer to structure for
  pack-job support with multiple components

Previous logic could fail on step allocation in larger job allocation

Underlying logic not yet available, just the new option parsing and
  documentation.

Make packjobid, packjoboffset, and packjobidset fields available in squeue
      output.

Test salloc/sbatch job options passed and resulting environment variables.

Improve backfill scheduling algorithm with respect to starting jobs as soon
    as possible while avoiding advanced reservations.
bug 3757

bug 3886

Not necessarily fatal(), but of potential interest when debugging
odd slurmctld crashes. Cannot go where the limit is originally set,
as the logging infrastructure is not avaiable at that point.

Bug 3886.

test1.91 fails with non-default binding

Bug 3581.

Fix for commit 250378c2
  test7.3 was failing without this patch
  bug 3502

test 17.12 was leaving slurm-#.out files around. Explicitly set
  output file to /dev/null and set time limit to 1 minute to avoid
  vestigial jobs.