tools: Add --resolve-kdc arg to engine-manage-domains

Adds --resolve-kdc argument to engine-mamage-domains which forces
discovery of kerberos servers using DNS. This is usefull, when LDAP and
Kerberos servers are not provided on same hosts (by default we suppose
that LDAP and Kerberos servers are on the same hosts).

Change-Id: I7884eae1c67636c7fc4578f7f16358205702ef64
Bug-Url: https://bugzilla.redhat.com/1031778
Signed-off-by: Martin Perina <mperina@redhat.com>