Abandon setting hairpin mode if finding the peer interface fails

Instead of setting it on every bridge-connected interface which may
have unwanted effects on unrelated things installed on the machine.

pkg/kubelet/network/hairpin/hairpin.go

@@ -58,8 +58,7 @@ func setUpContainerInternal(containerInterfaceName, containerDesc string, nsente
 	e := exec.New()
 	hostIfName, err := findPairInterfaceOfContainerInterface(e, containerInterfaceName, containerDesc, nsenterArgs)
 	if err != nil {
-		glog.Infof("Unable to find pair interface, setting up all interfaces: %v", err)
-		return setUpAllInterfaces()
+		return err
 	}
 	return setUpInterface(hostIfName)
 }
@@ -95,17 +94,6 @@ func findPairInterfaceOfContainerInterface(e exec.Interface, containerInterfaceN
 	return iface.Name, nil
 }
 
-func setUpAllInterfaces() error {
-	interfaces, err := net.Interfaces()
-	if err != nil {
-		return err
-	}
-	for _, netIf := range interfaces {
-		setUpInterface(netIf.Name) // ignore errors
-	}
-	return nil
-}
-
 func setUpInterface(ifName string) error {
 	glog.V(3).Infof("Enabling hairpin on interface %s", ifName)
 	ifPath := path.Join(sysfsNetPath, ifName)