OSHMEM: spml ikrit: fix mxm disconnect flow

Add out of band barrier before performing mxm disconnect.
It will make sure that every pe is ready to disconnect. Otherwise
bad things may happen.

oshmem/mca/spml/ikrit/spml_ikrit.c

@@ -345,6 +345,7 @@ int mca_spml_ikrit_del_procs(oshmem_proc_t** procs, size_t nprocs)
     opal_list_item_t *item;
     int my_rank = oshmem_my_proc_id();
 
+    oshmem_shmem_barrier();
 #if MXM_API >= MXM_VERSION(2,0)
     if (mca_spml_ikrit.bulk_disconnect) {
         mxm_ep_powerdown(mca_spml_ikrit.mxm_ep);