BUG/MEDIUM: mworker: don't reuse PIDs passed to the master

When starting the master worker with -sf or -st, the PIDs will be reused
on the next reload, which is a problem if new processes on the system
took those PIDs.

This patch ensures that we don't register old PIDs in the reload system
when launching the master worker.
diff --git a/src/haproxy.c b/src/haproxy.c
index cdb6066..a425744 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2444,6 +2444,13 @@
 	if (nb_oldpids)
 		nb_oldpids = tell_old_pids(oldpids_sig);
 
+	if ((getenv("HAPROXY_MWORKER_REEXEC") == NULL)) {
+		nb_oldpids = 0;
+		free(oldpids);
+		oldpids = NULL;
+	}
+
+
 	/* Note that any error at this stage will be fatal because we will not
 	 * be able to restart the old pids.
 	 */