golangci-lint round #3

this is the third round of preparing to use the golangci-lint on our
code base.

Signed-off-by: baude <bbaude@redhat.com>

pkg/firewall/iptables.go

@@ -151,7 +151,6 @@ type iptablesBackend struct {
 	protos         map[iptables.Protocol]*iptables.IPTables
 	privChainName  string
 	adminChainName string
-	ifName         string
 }
 
 // iptablesBackend implements the FirewallBackend interface