Fixes mxm endpoint destruction and hung during
SHMEM finalization.
Add a barrier between spml del procs and finalization.
Not having it caused hungs because ikrit spml can not properly
disconnect if its peer already finizalized.
Refs trac:3763
This commit was SVN r30572.
The following Trac tickets were found above:
Ticket 3763 --> https://svn.open-mpi.org/trac/ompi/ticket/3763