[EAP70] KUBE_PING produces many CLOSE_WAIT connections

KUBE_PING uses HttpURLConnection but not fully read err stream nor close streams and calling disconnect().

https://github.com/jboss-openshift/openshift-ping/blob/1.1.5.Final/common/src/main/java/org/openshift/ping/common/OpenshiftPing.java#L306

It makes a lot of CLOSE_WAIT connections, they remain until GC and leads "Too many open files" errors. This is pretty common pitfall, we can see a lot of artcles by searching HttpURLConnection and CLOSE_WAIT on the internet.

https://docs.oracle.com/javase/8/docs/api/java/net/HttpURLConnection.html

It'd be better to close them rather than relying on the error-prone pooling.