This commit add protection to the group, ob1, and bml endpoint lookup
code. For ob1 and the bml a lock has been added. For performance
reasons the lock is only held if a bml or ob1 endpoint does not
exist. ompi_group_dense_lookup no uses opal_atomic_cmpset to ensure
the proc is only retained by the thread that actually updates the
group.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>