for all nodes.  This will allow us to use tree communication for the
reattach RPC in sattach.

The srun, sbatch, and salloc --exclusive options now just set
"shared=0", and --shared sets "shared=1".  The second exclusive
variable appeared to be redundant.

Add --usage to sattach to quiet test16.1.

More command line option trimming.

completely anyway when the HP patch arrives...).