Fix authentication request in multidomain environment

[pviossat]

The modification fix an issue where the domain used to authenticate the target account is set to the querying user's domain.

For instance if myuser.users.domain.local wants to create shadow credential for mycomputer$.computers.domain.local by querying the computers.domain.local domain controller where mycomputer$ account is located, then the current code would generate authentication request for mycomputer$.users.domain.local. It would lead to an KDC_ERR_WRONG_REALM error.

The modification ensure the authentication request is done using the domain where the mycomputer$ object has been found. In the previous example the new code would generate authentication request for [email protected] as the LDAP request has been issued to the computers.domain.local domain controller.