fix(kube-peers): Add support for ExternalIP addresses
fix(kube-peers): Add support for ExternalIP addresses

Why:
* In some environments Nodes have an ExternalIP but no InternalIP

This change addresses the need by:
* Falling back to ExternalIP addresses if there isn't an InternalIP for a node

weaveworks/weave,weaveworks/weave,weaveworks/weave,weaveworks/weave