Fix for vanilla file services solution in a VC deployment when there is no cluster available in a datacenter

[BaluDontu]

What this PR does / why we need it:
Currently we fail if the datacenters doesn't have any clusters inside it - https://github.com/kubernetes-sigs/vsphere-csi-driver/blob/master/pkg/csi/service/common/vsphereutil.go#L518. But it is also possible to have ESX hosts directly inside the DC without a cluster. In that case it gives following error

2020-10-20T23:18:51.772Z ERROR common/vsphereutil.go:610 Error occurred while getting clusterComputeResource. error: cluster '*' not found {"TraceId": "d1141ed4-40ac-430a-885c-6b07fbf47189"}
sigs.k8s.io/vsphere-csi-driver/pkg/csi/service/common.getDsToFileServiceEnabledMap
/build/pkg/csi/service/common/vsphereutil.go:610
sigs.k8s.io/vsphere-csi-driver/pkg/csi/service/common.IsFileServiceEnabled
/build/pkg/csi/service/common/vsphereutil.go:567
sigs.k8s.io/vsphere-csi-driver/pkg/csi/service/common.GenerateDatastoreMapForFileVolumes
/build/pkg/csi/service/common/authmanager.go:240
sigs.k8s.io/vsphere-csi-driver/pkg/csi/service/common.(*AuthManager).refreshDatastoreMapForFileVolumes
/build/pkg/csi/service/common/authmanager.go:129
sigs.k8s.io/vsphere-csi-driver/pkg/csi/service/common.ComputeDatastoreMapForFileVolumes
/build/pkg/csi/service/common/authmanager.go:156

This function is internally called via IsFileServiceEnabled as part vanilla CSI controller init - https://github.com/kubernetes-sigs/vsphere-csi-driver/blob/master/pkg/csi/service/vanilla/controller.go#L133

since this is a valid deployment, this PR provides a fix for it.

This bug seems to exist from the time when vanilla file services solutions is released.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes # #455

Release note:

Fix for vanilla file services solution in a VC deployment when there is no cluster available in a datacenter

cc @divyenpatel @chethanv28

[divyenpatel]

/approve

[svcbot-qecnsdp]

Started vanilla file pipeline...

[chethanv28]

/ok-to-test

[chethanv28]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BaluDontu, chethanv28, divyenpatel

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• OWNERS [BaluDontu,chethanv28,divyenpatel]

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[svcbot-qecnsdp]

File vanilla build status: FAILURE 
Stage before exit: testbed-deploy 

[SandeepPissay]

The change looks good to me. Can you describe the testing done for this PR?

[svcbot-qecnsdp]

Started vanilla file pipeline...

[svcbot-qecnsdp]

File vanilla build status: FAILURE 
Stage before exit: testbed-deploy 

[svcbot-qecnsdp]

Started vanilla file pipeline...

[svcbot-qecnsdp]

File vanilla build status: FAILURE 
Stage before exit: e2e-tests 
Jenkins E2E Test Results: 
Ran 24 of 149 Specs in 2408.242 seconds
FAIL! -- 23 Passed | 1 Failed | 0 Pending | 125 Skipped
--- FAIL: TestE2E (2408.27s)
FAIL

Ginkgo ran 1 suite in 40m32.212036343s
Test Suite Failed
make: Leaving directory `/home/worker/workspace/github-csi-file-vanilla/Results/91/vsphere-csi-driver`

[divyenpatel]

/lgtm