Fix race in FirewalldInit

It was possible that signalHandler won't start because connections is
not assigned.

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

iptables/firewalld.go

@@ -2,9 +2,10 @@ package iptables
 
 import (
 	"fmt"
+	"strings"
+
 	"github.com/Sirupsen/logrus"
 	"github.com/godbus/dbus"
-	"strings"
 )
 
 type IPV string
@@ -40,6 +41,9 @@ func FirewalldInit() {
 	if err != nil {
 		logrus.Errorf("Failed to connect to D-Bus system bus: %s", err)
 	}
+	if connection != nil {
+		go signalHandler()
+	}
 
 	firewalldRunning = checkRunning()
 }
@@ -76,13 +80,11 @@ func (c *Conn) initConnection() error {
 
 	c.signal = make(chan *dbus.Signal, 10)
 	c.sysconn.Signal(c.signal)
-	go signalHandler()
 
 	return nil
 }
 
 func signalHandler() {
-	if connection != nil {
 	for signal := range connection.signal {
 		if strings.Contains(signal.Name, "NameOwnerChanged") {
 			firewalldRunning = checkRunning()
@@ -91,7 +93,6 @@ func signalHandler() {
 			reloaded()
 		}
 	}
-	}
 }
 
 func dbusConnectionChanged(args []interface{}) {