tdb: Factor out the retry loop from tdb_allrecord_upgrade

tdb: Factor out the retry loop from tdb_allrecord_upgrade

For the mutex code we will have to lock the hashchain and the record
lock area independently. So we will have to call the loop twice. And,
it's a small refactoring for the better anyway I think.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>