pg_upgrade: force timeline 1 in the new cluster

Previously, this prevented promoted standby servers from being upgraded
because of a missing WAL history file.  (Timeline 1 doesn't need a
history file, and we don't copy WAL files anyway.)

Report by Christian Echerer(?), Alexey Klyukin

Backpatch through 9.0

Author: bmomjian

src/bin/pg_upgrade/pg_upgrade.c

@@ -473,8 +473,9 @@ copy_clog_xlog_xid(void)
 	/* now reset the wal archives in the new cluster */
 	prep_status("Resetting WAL archives");
 	exec_prog(UTILITY_LOG_FILE, NULL, true,
-			  "\"%s/pg_resetxlog\" -l %s \"%s\"", new_cluster.bindir,
-			  old_cluster.controldata.nextxlogfile,
+			  /* use timeline 1 to match controldata and no WAL history file */
+			  "\"%s/pg_resetxlog\" -l 00000001%s \"%s\"", new_cluster.bindir,
+			  old_cluster.controldata.nextxlogfile + 8,
 			  new_cluster.pgdata);
 	check_ok();
 }