[cern] k8s: Clear cni configuration
cherry-picked from: https://review.opendev.org/#/c/669166/1
In fedora atomic 29, podman is present and configures its own cni. We need to clear the cni configuration otherwise we will get that cni0 is already used.
story: 2006171 task: 35682
Change-Id: Ic70938184bdb98eaaf4f384ce553818cf2624a2a Signed-off-by: Spyros Trigazis spyridon.trigazis@cern.ch