Xcluster-cni does not work for K8s < v1.16.0

[Lars Ekman]

The podCIDRs is assumed. Log printouts on K8s v1.15.10;

> kubectl logs -n kube-system   xcluster-cni-696z8
xcluster-cni; Fri Dec 13 19:30:54 CET 2019
K8S_NODE=[vm-005]
11:19:46: Generated /opt/cni/bin/podCIDR
11:19:46: K8s node address; 192.168.1.5
11:19:46: Using MTU=1480
11:19:46: Set addr 192.168.1.5/32 on dev sit0
xcluster-cni-router.sh: Using sit tunnels
xcluster-cni-router.sh: First node-info read
jq: error (at <stdin>:1): Cannot iterate over null (null)
jq: error (at <stdin>:1): Cannot iterate over null (null)
jq: error (at <stdin>:1): Cannot iterate over null (null)

[Lars Ekman]

Let's drop support for obsolete K8s versions