trust-fetch-domains: contact forest DCs when fetching trust domain info
    
    The code should always contact forest root DCs when requesting trust domain
    info. In the case of one-way or external trusts
    `com.redhat.idm.trust-fetch-domains` helper is leveraged, otherwise forest
    root domain is contacted directly through Samba using the credentials of HTTP
    principal.
    
    https://fedorahosted.org/freeipa/ticket/6328
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>