[Aggregator] Initialise sa_flags

valgrind complained about sa_flags being used uninitialised.

owlps-aggregator/owlps-aggregatord.c

@@ -32,6 +32,7 @@ int main(int argc, char **argv)
   initialise_configuration(argc, argv) ;
 
   /* Set up signal handlers */
+  action.sa_flags = 0 ;
   sigemptyset(&action.sa_mask) ;
   action.sa_handler = owl_sigint_handler ;
   sigaction(SIGINT, &action, NULL) ;