cgroup_escape() is a slight abuse of the cgroup code: what we really want
here is to escape the *current* process, whether it happens to be the LXC
monitor or not, into the / cgroups.

In the case of dump, we can't do an lxc_init(), because:

lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:993 - ##
lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:994 - # The container appears to be already running!
lxc 20160310103501.547 ERROR    lxc_commands - commands.c:lxc_cmd_init:995 - ##

We don't want to make this a command to send to the handler, because again,
cgroup_escape() is intended to escape the *current* task to the root
cgroups.

So, let's just have cgroup_escape() build its own handler when required.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>