Fix nil reference and handle hostname with prefix,suffix

This PR fixes mentioned in the issue https://github.com/foundation-model-stack/multi-nic-cni/issues/56.

need to also check nil value of route.Dst

    if route.Gw != nil && cmpRoute.Gw != nil && route.Dst != nil && cmpRoute.Dst != nil {
        if route.Dst.String() == cmpRoute.Dst.String() && route.Gw.String() == cmpRoute.Gw.String() {
            return true, nil
        }

In AWS machine, as nodename contains suffix of zone (e.g., ap-northeast-1.compute.internal), use Contains function intead of =.
```
> uname -n
ip-10-0-143-42 # nodename = ip-10-0-143-42.ap-northeast-1.compute.internal
```

Signed-off-by: Sunyanan Choochotkaew sunyanan.choochotkaew1@ibm.com

foundation-model-stack / multi-nic-cni

Fix nil reference and handle hostname with prefix,suffix #58