This fixes the race that happens in rktnetes when pod B invokes
'kubenet.SetUpPod()' before another pod A becomes actually running.
The second 'kubenet.SetUpPod()' call will not pick up the pod A
and thus overwrite the host port iptable rules that breaks pod A.
This PR fixes the case by listing all 'active pods' (all non-exited
pods) instead of only running pods.
5389a74388