CVE-2020-25718 s4-rpc_server: Provide wrapper samdb_confirm_rodc_allowed_to_repl_to()

CVE-2020-25718 s4-rpc_server: Provide wrapper samdb_confirm_rodc_allowed_to_repl_to()

This shares the lookup of the tokenGroups attribute.

There will be a new caller that does not want to do this step,
so this is a wrapper of samdb_confirm_rodc_allowed_to_repl_to_sid_list()
rather than part of it

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14558

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>