r25750: Update the objectclass module to improve consistency in Samba4.

r25750: Update the objectclass module to improve consistency in Samba4.

The aim here is to ensure that if we have

CN=Users,DC=samba,DC=example,DC=com

that we cannot have a DN of the form

cn=admin ,cn=useRS,DC=samba,DC=example,DC=com

This module pulls apart the DN, fixes up the relative DN part, and
searches for the parent to copy the base from.

I've used the objectclass module, as I intend to also validate the
placement of child objects, by reading the allowedChildClasses virtual
attribute.

In the future, I'll also force the attribute names to be consistant
(using the case from the schema).

Andrew Bartlett
(This used to be commit c0a0c69ac5a81cfcb7c7d5ba38db59f8686c30ab)