Factor out checkpointing with external namespace code
Factor out checkpointing with external namespace code

To checkpoint and restore a container with an external network namespace
(like with Podman and CNI), runc tells CRIU to ignore the network
namespace during checkpoint and restore.

This commit moves that code to their own functions to be able to reuse
the same code path for external PID namespaces which are necessary for
checkpointing and restoring containers out of a pod in cri-o.

Signed-off-by: Adrian Reber <9f82b3db7475afbb412180fe9fab7c69d6ece340@redhat.com>

opencontainers/runc,opencontainers/runc,opencontainers/runc,xiaochenshen/runc,rhatdan/runc,rhatdan/runc,mikebrow/runc,kolyshkin/runc,kolyshkin/runc,xiaochenshen/runc,estesp/runc,mikebrow/runc,opencontainers/runc,dqminh/runc,estesp/runc,dqminh/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,kolyshkin/runc,dqminh/runc,estesp/runc,rhatdan/runc,xiaochenshen/runc,mikebrow/runc