d/control: adjust package relationship between alternatives

If the iptables-nftables-package is installed with and old iptables package,
there will be a path clash. Let's prevent that with an explicit Break.

Anyway, iptables-nftables-package Depends on an specific version of iptables
due to dependencies.
Signed-off-by: Arturo Borrero Gonzalez <arturo@debian.org>

debian/control

@@ -189,6 +189,7 @@ Depends: arptables,
          ${shlibs:Depends}
 Recommends: nftables
 Suggests: kmod
+Breaks: iptables (<< 1.6.2-1)
 Description: iptables compat tools for nftables
  this package includes the compat tools to load iptables, ip6tables, arptables
  and ebtables rules to the nf_tables kernel subsystem.