Adds a mechanism in vSphere Cloud Provider to get credentials from Kubernetes secrets

[abrarshivani]

What this PR does / why we need it:
Currently, vCenter credentials are stored in plain text in vsphere.conf. This PR adds a mechanism in vSphere Cloud Provider to get vCenter credentials from Kubernetes secrets.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:
Internally review here: vmware-archive#484
Workflow:

1. Create vsphere.conf file with secret-name and secret-namespace.

   [Global]
   insecure-flag = 1
   secret-name = "vcconf"
   secret-namespace = "kube-system"
   
   [VirtualCenter "10.160.45.119"]
   port = 443
   datacenters = k8s-dc-1
   
   [Workspace]
   server = 10.160.45.119
   datacenter = k8s-dc-1
   default-datastore = sharedVMFS-0
   folder = Discovered virtual machine
   

2. Launch Kubernetes cluster with vSphere Cloud Provider Configured.

3. Create secret with vCenter credentials.
   a. Create base64 encoding for username and password:
   username:

   	> echo -n 'admin' | base64
   	YWRtaW4= 
   

   password:

   	> echo -n 'vsphere' | base64
   	dnNwaGVyZQ==
   

   b. kubectl create -f vccredentials.yaml

   	#vccredentials.yaml
   	apiVersion: v1
   	kind: Secret
   	metadata:
   		name: vcconf
   	type: Opaque
   	data:
   		10.192.44.199.username: YWRtaW4=
   		10.192.44.199.password: dnNwaGVyZQ==
   

4. vSphere Cloud Provider can be used now.

Note:
Secrets info can be provided with both (old and new) vSphere Cloud provider configuration formats.

Tests Done:

• vSphere Cloud Provider unit test.
• Volume lifecyle with Username and Password in vsphere.conf (for backward compability)
• Volume lifecyle with secrets information in vsphere.conf.
• Update secrets workflow

Release note:

Adds a mechanism in vSphere Cloud Provider to get credentials from Kubernetes secrets

[abrarshivani]

//cc @kubernetes/vmware

[abrarshivani]

/retest

[abrarshivani]

/retest

[divyenpatel]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: abrarshivani, divyenpatel

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• pkg/cloudprovider/providers/vsphere/OWNERS [abrarshivani,divyenpatel]

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[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 63969, 63902, 63689, 63973, 63978). If you want to cherry-pick this change to another branch, please follow the instructions here.

[dkirrane]

Question is this available as part of K8s 1.10.3?

And can the Secret be Global i.e. not for specific VirtualCenter:

[Global]
insecure-flag = 1
secret-name = "vcconf"
secret-namespace = "kube-system"

	apiVersion: v1
	kind: Secret
	metadata:
		name: vcconf
	type: Opaque
	data:
		username: YWRtaW4=
		password: dnNwaGVyZQ==