In-cluster config builder does not work properly in an ipv6 cluster

[liggitt]

java/util/src/main/java/io/kubernetes/client/util/ClientBuilder.java

Lines 206 to 208 in cbc1d38

	final String host = System.getenv(ENV_SERVICE_HOST);
	final String port = System.getenv(ENV_SERVICE_PORT);
	builder.setBasePath("https://" + host + ":" + port);

assumes a DNS name or ipv4 address... it does not work correctly with an ipv6 address (the ipv6 host must be wrapped in brackets)

[liggitt]

cc @thockin

[brendandburns]

Thanks for reporting, will send a PR.