Upgrading to Docker 1.7.0 on Ubuntu 14.04 will screw up containers by default

Just got bitten by this one, upgrading a default ubuntu installation of lxc-docker from 1.6.0:

  > sudo tail /var/log/upstart/docker.log
  ERRO[0000] [graphdriver] prior storage driver "devicemapper" failed: driver not supported 
  FATA[0000] Error starting daemon: error initializing graphdriver: driver not supported 
  /var/run/docker.sock is up
  ERRO[0000] Udev sync is not supported. This will lead to unexpected behavior, data loss and errors. For more information, see https://docs.docker.com/reference/commandline/cli/#daemon-storage-driver-option