s4:tests/dirsync: add tests for dirsync with extended_dn

s4:tests/dirsync: add tests for dirsync with extended_dn

This demonstrates a problems that the extended_dn returned
by the dirsync module always uses the SDDL format for GUID/SID
components.

Azure AD connect reports discovery errors:
  reference-value-not-ldap-conformant
for attributes member and manager.
The key is that it sends the LDAP_SERVER_EXTENDED_DN_OID without
an ExtendedDNRequestValue blob, which means the flag value should
be treated as 0 and the HEX string format should be used.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14153

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>