log: add LOG_DEBUG message on restarting stratum.

util.c

@@ -2422,12 +2422,15 @@ out:
 
 bool restart_stratum(struct pool *pool)
 {
+	applog(LOG_DEBUG, "Restarting stratum on pool %s", pool->poolname);
+
 	if (pool->stratum_active)
 		suspend_stratum(pool);
 	if (!initiate_stratum(pool))
 		return false;
 	if (!auth_stratum(pool))
 		return false;
+
 	return true;
 }