Merge branch 'upstream-bugfix' of https://github.com/lxc/lxc

Merge branch 'upstream-bugfix' of https://github.com/lxc/lxc

* 'upstream-bugfix' of https://github.com/lxc/lxc: (47 commits)
  replace HOOK define with proper code.
  Remove lxc-start-ephemeral from configure.ac
  revert devtmpfs in ubuntu templates
  lxc-ubuntu{-cloud}: Fix missing "fi" in new devtmpfs code
  fix "make rpm"
  display warning when yum missing in fedora template
  templates: mount devtmpfs in ubuntu containers
  handle clone of btrfs snapshots
  if the rootfs is a btrfs subvolume, delete it instead of rm -rf
  lxc-debian: replace isc-dhcp-server by isc-dhcp-client
  lxc-ls: Scan cgroup mount points from fstype and not device
  Allow short -h and -n options to lxc-ps
  lxc-ubuntu: fix printing of default user
  lxc-debian: specify isc-dhcp-server in package list
  try to better handle out of date container caches.
  link /dev/kmsg to /dev/console in the container
  lxc-clone: fix the '--name' parameter
  lxc-ls: Use readlink on $directory
  lxc-busybox: Use relative mounts in lxc.mount.entry
  busybox: for all lib dirs create mounts only if directories exist
  ...

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>