Admission controller should detect if `cniVersion` is not present

[dougbtv]

E.g. to prevent:

Oct 27 14:58:01 worker-0 crio[2934]: time="2020-10-27 14:58:01.780170471Z" level=info msg="About to del CNI network multus-cni-network (type=multus)"
Oct 27 14:58:01 worker-0 crio[2934]: time="2020-10-27 14:58:01.865939294Z" level=error msg="Error deleting network: delegateDel: error invoking DelegateDel - \"egress-router\": error in getting result from DelNetwork: invalid version \"\": the version is empty"