[PATCH] IPA subdomains - ask for information about master domain

[Jan Zelený]

This functionality will be utilized by PAC responder once it lands in the 
master branch. One round of review already done by Sumit. Also the patch has 
been tested together with the PAC responder.

The query is performed only if there is missing information in the
cache. That means this should be done only once after restart when cache
doesn't exist. All subsequent requests for subdomains won't include the
request for master domain. This is done to save time since it is not possible 
to change this information once IPA server is installed.

https://fedorahosted.org/sssd/ticket/1351

Thanks
Jan