Fix a message to only show when log_info is requested and the verbose

flag is set.
This is because it needs a calculation that is only done when the
verbose flag is set, so if i have requested log INFO level but haven't
set the flag it shows a null

repmgr.c

@@ -1043,6 +1043,7 @@ stop_backup:
 	}
 	last_wal_segment = PQgetvalue(res, 0, 0);
 
+	if (runtime_options.verbose)
 	log_info(_("%s requires primary to keep WAL files %s until at least %s\n"),
 	         progname, first_wal_segment, last_wal_segment);