KRB5: Adding DNS SRV lookup for krb5 provider
This patch add DNS SRV lookup for krb5 provider.
Resolves:
https://fedorahosted.org/sssd/ticket/2888
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
(cherry picked from commit 684191e61d891b1c34f3742a40d5a2ed6a1192dd)
(cherry picked from commit dd5a52db9653d83bef26da468157c216df45f715)