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>