The cgroup dependency brings in quite a lot only for WithNamespaceCgroupDeletion,
which is a namespaces.DeleteOpt.
Signed-off-by: Tibor Vass <tibor@docker.com>
Closes#3305
This adds an opt and a `--cgroup,-c` flag to `ctr namespaces rm` to
remove the cgroup that is commonly created with runtimes.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>