Vendor in latest containers storage

We want to get support into skopeo for handling
override_kernel_checks so that we can use overlay
backend on RHEL.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

vendor/github.com/containers/storage/pkg/mount/mountinfo.go

@@ -38,3 +38,17 @@ type Info struct {
 	// VfsOpts represents per super block options.
 	VfsOpts string
 }
+
+type byMountpoint []*Info
+
+func (by byMountpoint) Len() int {
+	return len(by)
+}
+
+func (by byMountpoint) Less(i, j int) bool {
+	return by[i].Mountpoint < by[j].Mountpoint
+}
+
+func (by byMountpoint) Swap(i, j int) {
+	by[i], by[j] = by[j], by[i]
+}