Protect the base PTL close against multiple call of close. The problem came mainly from the

fact that we have several PML and that each one will call the PTL close in their own
close function.

This commit was SVN r6360.

ompi/mca/ptl/base/ptl_base_close.c

@@ -59,10 +59,14 @@ int mca_ptl_base_close(void)
   }
 
   /* cleanup */
-  if(NULL != mca_ptl_base_include)
+  if( NULL != mca_ptl_base_include ) {
      free(mca_ptl_base_include);
-  if(NULL != mca_ptl_base_exclude)
+     mca_ptl_base_include = NULL;
+  }
+  if( NULL != mca_ptl_base_exclude ) {
      free(mca_ptl_base_exclude);
+     mca_ptl_base_exclude = NULL;
+  }
 
   /* restore event processing */
   opal_event_enable();