Feat firewall controller interface (#740)

Add a standard interface for the client firewall to support ACL.

client/firewall/iptables/rule.go

@@ -0,0 +1,13 @@
+package iptables
+
+// Rule to handle management of rules
+type Rule struct {
+	id    string
+	specs []string
+	v6    bool
+}
+
+// GetRuleID returns the rule id
+func (r *Rule) GetRuleID() string {
+	return r.id
+}