Create server-dns sub-package.
    
    This allows us to automatically pull in package bind-pkcs11
    and thus create upgrade path for on CentOS 7.1 -> 7.2.
    
    IPA previously had no requires on BIND packages and these had to be
    installed manually before first ipa-dns-install run.
    We need to pull additional bind-pkcs11 package during RPM upgrade
    so ipa-dns-install cannot help with this.
    
    https://fedorahosted.org/freeipa/ticket/4058
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>