Integrate realmdomains with IPA DNS

Add an entry to realmdomains when a DNS zone is added to IPA.
Delete the related entry from realmdomains when the DNS zone is deleted
from IPA.

Add _kerberos TXT record to DNS zone when a new realmdomain is added.
Delete _kerberos TXT record from DNS zone when realmdomain is deleted.

Add unit tests to cover new functionality.

https://fedorahosted.org/freeipa/ticket/3544
Update only selected attributes for winsync agreement

Trying to insert nsDS5ReplicatedAttributeListTotal and
nsds5ReplicaStripAttrs to winsync agreements caused upgrade errors.
With this patch, these attributes are skipped for winsync agreements.

Made find_ipa_replication_agreements() in replication.py more
corresponding to find_replication_agreements. It returns list of
entries instead of unicode strings now.

https://fedorahosted.org/freeipa/ticket/3522
Require new samba and krb5

Require samba 4.0.5 (passdb API changed). Make sure that we use the
right epoch number with samba so that the Requires is correctly
enforced.

Require krb5 1.11.2-1 to fix missing PAC issue.

Also fix backup dir permissions.
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