move some duplicated logic into a common function

    nodes already in another reservation.

  from the database

we're able to handle this now with the new logic that tests scheduling with 
preempted jobs removed from our simulated scheduling matrix

  This adds job preemption support to select/linear for preempt/qos and 
  optimizes job placement on nodes considering workload from other partitions.

svn merge https://eris.llnl.gov/svn/slurm/trunk https://eris.llnl.gov/svn/slurm/branches/slurm-1.4.srun.hang

I merged changes from the trunk onto slurm-1.4.srun.hang branch as I worked,
so the branch was up to date with ongoing trunk development.  The merge
command above finds the diffs between the trunk and branch--just the development
for the branch--and applies the changes to the trunk.