We're setting up a new cluster here. Open MPI 1.7.4 was hanging at
startup without any error message. The issue appears to be
udcm_component_query() hanging in finalize() on the sched_yield() loop
when memlock limit isn't set to unlimited as usual.
Unfortunately the hangs occur before we print the usual error message
"you need to set memlock limit to unlimited". If the udcm problem cannot
be fixed, it would be good to print an error message about memlock not
being unlimited much earlier.