ompi/communicator: set grp_instance for leader_group

when constructing the leader_group in intercomm_create_from_groups, make sure to set the grp_instance on the leader_group, otherwise the memkind operations trying to acces the info from the instance fails.

Signed-off-by: Edgar Gabriel <edgar.gabriel@amd.com>

ompi/communicator/comm.c

@@ -1796,6 +1796,7 @@ int ompi_intercomm_create_from_groups (ompi_group_t *local_group, int local_lead
             }
 
             leader_group = ompi_group_allocate_plist_w_procs (NULL, leader_procs, 2);
+            leader_group->grp_instance = local_group->grp_instance;
             ompi_set_group_rank (leader_group, my_proc);
             if (OPAL_UNLIKELY(NULL == leader_group)) {
                 free(leader_procs);