Automatic merge from submit-queue (batch tested with PRs 46441, 43987, 46921, 46823, 47276)

kubelet/network: report but tolerate errors returned from GetNetNS() v2

Runtimes should never return "" and nil errors, since network plugin
drivers need to treat netns differently in different cases. So return
errors when we can't get the netns, and fix up the plugins to do the
right thing.

Namely, we don't need a NetNS on pod network teardown. We do need
a netns for pod Status checks and for network setup.

V2: don't return errors from getIP(), since they will block pod status :(  Just log them.  But even so, this still fixes the original problem by ensuring we don't log errors when the network isn't ready.

@freehan @yujuhong 

Fixes: https://github.com/kubernetes/kubernetes/issues/42735
Fixes: https://github.com/kubernetes/kubernetes/issues/44307