Integrate KUBE_PING discovery protocol

KUBE_PING is a discovery protocol for JGroups cluster nodes managed by Kubernetes. Since Kubernetes is in charge of launching nodes, it knows the IP addresses of all pods it started, and is therefore the best place to ask for cluster discovery. Discovery is done by asking Kubernetes for a list of IP addresses of all cluster nodes.

Given OpenShift is based on Kubernetes KUBE_PING, it is an ideal fit.

A separate integration is needed besides just JGroups upgrade. Historically all protocols were bundled within main jgroups-<version>.jar. Since the main JGroups project does not allow runtime dependencies, protocols had to include a lot of unmaintainable copy-pasted and trimmed library code. This hinders supportability. Protocols needing to fetch dependencies now reside in separate repository in the https://github.com/jgroups-extras repository. As such, KUBE_PING resides in https://github.com/jgroups-extras/jgroups-kubernetes repository.

Note that the OpenShift team currently maintain their own implementation of PING protocols to be used in OpenShift. See the https://github.com/jboss-openshift/openshift-ping repository.