btrfs via symlink not working

# fresh quantal instance (2012-09-04)
sudo apt-get update
sudo apt-get install lxc btrfs-tools -y </dev/null

# put a btrfs fs on /mnt
sudo umount /mnt
dev=$(awk '$2 == "/mnt" { print $1; }' /etc/fstab)
echo "making fs on $dev"
sudo mkfs -t btrfs $dev -L ephemeral0 $dev
sudo mount /mnt

sudo mkdir /var/lib/lxc /var/cache/lxc # in case they dont already exist

sudo rsync -a /var/lib/lxc/ /mnt/var-lib-lxc
sudo rm -Rf /var/lib/lxc
sudo ln -sf /mnt/var-lib-lxc /var/lib/lxc

sudo rsync -a /var/cache/lxc/ /mnt/var-cache-lxc
sudo rm -Rf /var/cache/lxc
sudo ln -sf /mnt/var-cache-lxc /var/cache/lxc

sudo lxc-create -t ubuntu-cloud -n source-precise-amd64 -- --release precise --arch amd64 --stream daily
sudo lxc-clone -o source-precise-amd64 -n precise-amd64
sudo lxc-start -n precise-amd64 -d
sleep 10
sudo lxc-stop -n precice-amd64
sleep 10

## Then ##

$ sudo lxc-destroy -n precise-amd64
rm: cannot remove `//var/lib/lxc/precise-amd64/rootfs': Directory not empty
rm: skipping `/var/lib/lxc/precise-amd64/rootfs', since it's on a different device

I would have expected this to work.

$ sudo lxc-ls
precise-amd64 source-precise-amd64

I'm not sure what creates this scenario, but some more debug:

$ df /var/lib/lxc/precise-amd64
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vdb 20971520 727396 18217108 4% /mnt

$ df /var/lib/lxc/precise-amd64/rootfs
Filesystem 1K-blocks Used Available Use% Mounted on
- 20971520 727396 18217108 4% /mnt/var-lib-lxc/precise-amd64/rootfs

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: lxc 0.8.0~rc1-4ubuntu32
ProcVersionSignature: User Name 3.5.0-13.14-generic 3.5.3
Uname: Linux 3.5.0-13-generic x86_64
ApportVersion: 2.5.1-0ubuntu4
Architecture: amd64
Date: Wed Sep 5 00:48:33 2012
Ec2AMI: ami-00000146
Ec2AMIManifest: FIXME
Ec2AvailabilityZone: nova
Ec2InstanceType: m1.small
Ec2Kernel: unavailable
Ec2Ramdisk: unavailable
ProcEnviron:
 TERM=screen
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: lxc
UpgradeStatus: No upgrade log present (probably fresh install)