Release the default base on finalize.

This commit was SVN r20562.

opal/event/event.c

@@ -386,6 +386,10 @@ int opal_event_fini(void)
     if (NULL != opal_event_module_include) {
         opal_argv_free(opal_event_module_include);
     }
+    if( NULL != opal_current_base ) {
+        event_base_free(opal_current_base);
+        opal_current_base = NULL;
+    }
     return OPAL_SUCCESS;
 }