btl/scif: prevent SIGSEGV from occuring when the module is unloaded

Fixes trac:4615

cmr=v1.8.2:reviewer=hjelmn

This commit was SVN r31717.

The following Trac tickets were found above:
  Ticket 4615 --> https://svn.open-mpi.org/trac/ompi/ticket/4615

ompi/mca/btl/scif/btl_scif_module.c

@@ -125,6 +125,8 @@ mca_btl_scif_module_finalize (struct mca_btl_base_module_t *btl)
 
     /* close the listening endpoint */
     if (-1 != mca_btl_scif_module.scif_fd) {
+        pthread_cancel(mca_btl_scif_module.listen_thread);
+        pthread_join(mca_btl_scif_module.listen_thread, NULL);
         scif_close (mca_btl_scif_module.scif_fd);
     }