s4:dirsync: fix interaction of dirsync and extended_dn controls

s4:dirsync: fix interaction of dirsync and extended_dn controls

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
RN: Prevent azure ad connect from reporting discovery errors:
reference-value-not-ldap-conformant

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Thu Oct 24 11:06:58 UTC 2019 on sn-devel-184

(cherry picked from commit d0f566c4ad32d69a1cf896e2dde56fc2489bb7fc)