Add iptables rules for ns_IPaddr2

Add new parameters for ns_IPaddr2 resource:
  - iptables_start_rules - rules we want to add on VIP start
  - iptables_stop_rules - rules we want to remove on VIP stop
  - iptables_comment - comment to associate with new rules

Use this new parameters in order to fix outgoing IP (src ip) in
packets routed via default route from "haproxy" namespace.

Change-Id: I4c58612ea3bd3401000939b098d90d14a85acad1
Closes-bug: #1321466