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* Rootfs dir is created during container creation not during bundle
  creation
* Add support for v2
* UnmountAll is a no-op when the path to unmount (i.e. the rootfs dir)
  does not exist or is invalid

Co-authored-by: Danail Branekov <danailster@gmail.com>
Signed-off-by: Georgi Sabev <georgethebeatle@gmail.com>

mount/mount_linux.go

@@ -112,6 +112,9 @@ func unmount(target string, flags int) error {
 // are no mounts remaining (EINVAL is returned by mount), which is
 // useful for undoing a stack of mounts on the same mount point.
 func UnmountAll(mount string, flags int) error {
+	if _, err := os.Stat(mount); err != nil {
+		return nil
+	}
 	for {
 		if err := unmount(mount, flags); err != nil {
 			// EINVAL is returned if the target is not a