python:tests: Allocate OID range for testing to avoid collisions

python:tests: Allocate OID range for testing to avoid collisions

sid_strings.py used the same OID range as ldap_schema.py, which
occasionally led to test failures when the same OID was generated twice.
Using a different range, and making use of the expected RID if we have
it, should reduce the likelihood of collisions.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Thu Aug 25 13:55:47 UTC 2022 on sn-devel-184