c api: send lxcpath to destroy command

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
cgpath: send container name to nrtasks

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

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
lxc-destroy: add --lxc-path argument

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