Change to aggregator so it calls a user apiservice via its pod IP.

proxy_handler now uses the endpoint router to map the cluster IP to
appropriate endpoint (Pod) IP for the given resource.
Added code to allow aggregator routing to be optional.
Updated bazel build.
Fixes to cover JLiggit comments.
Added util ResourceLocation method based on Listers.
Fixed issues from verification steps.
Updated to add an interface to obfuscate some of the routing logic.
Collapsed cluster IP resolution in to the aggregator routing
implementation.
Added 2 simple unit tests for ResolveEndpoint

cluster/gce/container-linux/configure-helper.sh

@@ -810,6 +810,7 @@ function start-kube-apiserver {
   params+=" --tls-cert-file=/etc/srv/kubernetes/server.cert"
   params+=" --tls-private-key-file=/etc/srv/kubernetes/server.key"
   params+=" --token-auth-file=/etc/srv/kubernetes/known_tokens.csv"
+  params+=" --enable-aggregator-routing=true"
   if [[ -n "${KUBE_PASSWORD:-}" && -n "${KUBE_USER:-}" ]]; then
     params+=" --basic-auth-file=/etc/srv/kubernetes/basic_auth.csv"
   fi