Update Kubernetes proxy URLs

[ShawnZhong]

Fix #3404

Follow the Kubernetes proxy URLs documented here (Note that proxy is placed after the service name instead of /api/v1):

http://kubernetes_master_address/api/v1/namespaces/namespace_name/services/service_name[:port_name]/proxy

[ShawnZhong]

Note that the helm configuration file at https://storage.googleapis.com/heron-charts needs to be updated as well. Otherwise, users following the helm guide will not be able to get any stats from heron UI.

I believe the file has already been updated in this repository (see below), but the file at https://storage.googleapis.com/heron-charts was not changed for a while (The last modified time is 2018-04-18).

incubator-heron/deploy/kubernetes/helm/templates/tools.yaml

Lines 109 to 115 in d8db1c5

	command: ["sh", "-c"]
	args:
	- >-
	heron-ui
	--port=8889
	--base_url={{ .Values.heron.url }}
	- name: heron-apiserver

[joshfischer1108]

Looks good to me. I thought we updated these URLs a while ago. Thanks for catching and fixing this @ShawnZhong

[joshfischer1108]

I'm going to let this sit for a day and see if anyone else has any feedback.

[nwangtw]

I am not familiar with this part but the change looks reasonable. Thanks.

Please feel free to merge.