freezer: add option to specify that the caller is the lxc-start monitor

Because the stop callback handler in the monitor calls do-unfreeze
after stopping the container (to allow 'freeze; kill' to DTRT).
Usually unfreeze follows up by sending a state update to the
monitor, but don't do that after a stop.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
implement cgmanager_remove_cgroup

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
lxc.conf: note the 'lxc.network.type = none'  option

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>