Revert "snapshot/storage: namespace snapshot drivers"

This reverts commit b1a70aa335.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

snapshot/btrfs/btrfs_test.go

@@ -12,7 +12,6 @@ import (
 	"testing"
 
 	"github.com/containerd/containerd/mount"
-	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/snapshot"
 	"github.com/containerd/containerd/snapshot/testsuite"
 	"github.com/containerd/containerd/testutil"
@@ -51,7 +50,7 @@ func TestBtrfs(t *testing.T) {
 
 func TestBtrfsMounts(t *testing.T) {
 	testutil.RequiresRoot(t)
-	ctx := namespaces.WithNamespace(context.Background(), "snapshotter-btrfs-test")
+	ctx := context.Background()
 
 	// create temporary directory for mount point
 	mountPoint, err := ioutil.TempDir("", "containerd-btrfs-test")