1. Replace EnsureRemoveAll() with Rmdir(), as here we are removing
the container's mount point, which is already properly unmounted
and is therefore an empty directory.
2. Ignore the Rmdir() error (but log it unless it's ENOENT). This
is a mount point, currently unmounted (i.e. an empty directory),
and an older kernel can return EBUSY if e.g. the mount was
leaked to other mount namespaces.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
732dd9b848