Description of problem:
lxc-start fails when cgroups are mounting the 'all' controller

Version-Release number of selected component (if applicable):
# rpm -q lxc libcgroup docker-io
lxc-0.9.0-2.el6.x86_64
libcgroup-0.40.rc1-5.el6.x86_64
docker-io-0.7.0-14.el6.x86_64

How reproducible:
very

Steps to Reproduce:
1. set up /etc/cgconfig.conf like

mount {
#       cpuset  = /cgroup/all;
        cpu     = /cgroup/all;
        cpuacct = /cgroup/all;
        memory  = /cgroup/all;
#       devices = /cgroup/all;
        freezer = /cgroup/all;
        net_cls = /cgroup/all;
#       blkio   = /cgroup/all;
}
2. start the docker server in one terminal `docker -d`
3. then `docker run -i -t mattdm/fedora /bin/bash`

Actual results:
lxc-start: cgroup is not mounted                                                
lxc-start: Error setting devices.deny to a for lxc/15509c8f85901ba2fc2cb883d777b836cee7cdeb2b46d6ebc07d9a1a5b1de0f0 
lxc-start: failed to setup the cgroups for '15509c8f85901ba2fc2cb883d777b836cee7cdeb2b46d6ebc07d9a1a5b1de0f0' 
lxc-start: failed to spawn '15509c8f85901ba2fc2cb883d777b836cee7cdeb2b46d6ebc07d9a1a5b1de0f0' 
lxc-start: Device or resource busy - failed to remove cgroup '/cgroup/all/lxc/15509c8f85901ba2fc2cb883d777b836cee7cdeb2b46d6ebc07d9a1a5b1de0f0'


Expected results:
a bash shell

Additional info:
opened an upstream bug for this support https://github.com/lxc/lxc/issues/110