Update libcontainer to 29363e2d2d7b8f62a5f353be333

Signed-off-by: Michael Crosby <michael@docker.com>
Merge pull request #7597 from crosbymichael/update-libcontainer-aug4

Update libcontainer to 29363e2d2d7b8f62a5f353be333
Fixes "note" blockquote too long [doc, minor]

A "note" block includes too much text, so if you skip over it the next paragraph makes zero sense.
Merge pull request #7610 from remram44/patch-1

Fixes "note" blockquote too long [doc, minor]