all job priorities are very low.

 I'll need to modify the test for systems with >1 ThreadPerCore configured

  found in testing that new code:
- avoid draining node if stdout/err file can't be created
- correction in logic for >1 thread per core in setting a job's SLURM_CPUS_ON_NODE env var
- Fix for uneven task distributions on heterogeneous clusters
  (e.g. 4 CPUs on the first node and 2 CPUs on the second,
  a task_count=2 resulted in cpus_per_task=3, and previously
  allocated both tasks to the first node, now does one task
  per node)

  (was using day of month=0 instead of 1) 

 Mostly a matter of moving some logic to a new module.

Changed the default age weight to zero in the mf plugin

  affinity bits don't get cleared by default for direct use of the launch API
  (as used by poe). 
If a zero value is registerd for task launch, reset to 1 and avoid an empty bitmap
  and subsequent task binding error.

   otherwise a batch job is unable to create an sgi_jobs container for the
   proctrack/sgi_jobs plugin

Revise task exit log messages from slurmstepd to be clearer,
and include the termination signal if WIFSIGNALED, and a
message "(core dumped)" if a corefile was generated. The
extra timestamp is also removed.