tdb: Update times in tdb_transaction_commit per fd, not per name

tdb: Update times in tdb_transaction_commit per fd, not per name

We might have a relative filename in tdb->name, so we might do the
wrong thing here. And as we have the fd, why not use it...

We call futimens in vfs_default without #ifdef and it's Posix 2018 or
before. So I don't think we need to check for it.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>