Move HostUtil to pkg/volume/util/hostutil

This patch moves the HostUtil functionality from the util/mount package
to the volume/util/hostutil package.

All `*NewHostUtil*` calls are changed to return concrete types instead
of interfaces.

All callers are changed to use the `*NewHostUtil*` methods instead of
directly instantiating the concrete types.

pkg/kubelet/kubelet_pods_windows_test.go

@@ -20,9 +20,9 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
-	"k8s.io/kubernetes/pkg/util/mount"
+	"k8s.io/kubernetes/pkg/volume/util/hostutil"
 	"k8s.io/kubernetes/pkg/volume/util/subpath"
 )
 
@@ -82,7 +82,7 @@ func TestMakeMountsWindows(t *testing.T) {
 		},
 	}
 
-	fhu := &mount.FakeHostUtil{}
+	fhu := hostutil.NewFakeHostUtil(nil)
 	fsp := &subpath.FakeSubpath{}
 	mounts, _, _ := makeMounts(&pod, "/pod", &container, "fakepodname", "", "", podVolumes, fhu, fsp, nil)