Convert for util.IP to just use a net.IP

pflag can handle IP addresses so use the pflag code instead of doing it
ourselves. This means our code just uses net.IP and we don't have all of
the useless casting back and forth!

contrib/mesos/pkg/executor/service/service.go

@@ -96,7 +96,7 @@ func NewKubeletExecutorServer() *KubeletExecutorServer {
 	} else {
 		k.RootDirectory = pwd // mesos sandbox dir
 	}
-	k.Address = util.IP(net.ParseIP(defaultBindingAddress()))
+	k.Address = net.ParseIP(defaultBindingAddress())
 	k.ShutdownFD = -1 // indicates unspecified FD
 
 	return k
@@ -404,7 +404,7 @@ func (ks *KubeletExecutorServer) createAndInitKubelet(
 	dconfig := bindings.DriverConfig{
 		Executor:         exec,
 		HostnameOverride: ks.HostnameOverride,
-		BindingAddress:   net.IP(ks.Address),
+		BindingAddress:   ks.Address,
 	}
 	if driver, err := bindings.NewMesosExecutorDriver(dconfig); err != nil {
 		log.Fatalf("failed to create executor driver: %v", err)
@@ -427,7 +427,7 @@ type kubeletExecutor struct {
 	*kubelet.Kubelet
 	initialize      sync.Once
 	driver          bindings.ExecutorDriver
-	address         util.IP
+	address         net.IP
 	dockerClient    dockertools.DockerInterface
 	hks             hyperkube.Interface
 	kubeletFinished chan struct{}   // closed once kubelet.Run() returns