The docker runtime doesn't tear down networking when GC-ing pods.
rkt already does so make docker do it too. To ensure this happens,
networking is always torn down for the container even if the
container itself is not deleted.
This prevents IPAM from leaking when the pod gets killed for
some reason outside kubelet (like docker restart) or when pods
are killed while kubelet isn't running.
Fixes: https://github.com/kubernetes/kubernetes/issues/14940
Related: https://github.com/kubernetes/kubernetes/pull/35572
Automatic merge from submit-queue
Made tracing of calls and container lifecycle steps in FakeDockerClient optional
Fixes#39717
Slightly refactored the FakeDockerClient code and made tracing optional (but enabled by default).
@yujuhong @Random-Liu
