Only selectable when specifically requested via "-mca odls pspawn"
Note that there are several concerns:
* we aren't getting SIGCHLD calls when the procs terminate
* we aren't seeing the IO pipes close on termination, though
we are getting output forwarded to mpirun
* I haven't found a way to bind the child process prior to exec.
If we want to use this method, we probably need someone to
implement a cgroup component for the orte/rtc framework
Signed-off-by: Ralph Castain <rhc@open-mpi.org>
