btl/scif: use safe syntax

Thanks to Ashley Pittman for pointing the modex should now be zero'ed

cmr=v1.8.2:ticket=trac:4871

This commit was SVN r32568.

The following Trac tickets were found above:
  Ticket 4871 --> https://svn.open-mpi.org/trac/ompi/ticket/4871

opal/mca/btl/scif/btl_scif_component.c

@@ -209,6 +209,7 @@ static void mca_btl_scif_autoset_leave_pinned (void) {
 static int mca_btl_scif_modex_send (void)
 {
     mca_btl_scif_modex_t modex;
+    memset(&modex, 0, sizeof(mca_btl_scif_modex_t));
     modex.port_id = mca_btl_scif_module.port_id;
 
     return opal_modex_send (&mca_btl_scif_component.super.btl_version, &modex, sizeof (modex));