fix vSphere client not using the provided custom CA bundle

[lsviben]

What this PR does / why we need it:
Fix the vSphere client issue where it doesnt use the provided custom CA bundle. Based on vmware/govmomi#1200.

Which issue(s) this PR fixes (optional, in fixes #<issue number> format, will close the issue(s) when PR gets merged):
Fixes #966

Optional Release Note:

Fixed vSphere client not using the provided custom CA bundle

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 2e82277838ade94dae0ab8c4d762a083d745eacd

[lsviben]

/retest

[xrstf]

/override pull-machine-controller-e2e-azure

[kubermatic-bot]

@xrstf: Overrode contexts on behalf of xrstf: pull-machine-controller-e2e-azure

In response to this:

/override pull-machine-controller-e2e-azure

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[kron4eg]

/approve

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kron4eg, lsviben

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• OWNERS [kron4eg]

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[lsviben]

/cherry-pick release/v1.27

[kubermatic-bot]

@lsviben: #969 failed to apply on top of branch "release/v1.27":

Applying: fix vSphere client not using the provided custom CA bundle
Using index info to reconstruct a base tree...
M	pkg/cloudprovider/provider/vsphere/client.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/cloudprovider/provider/vsphere/client.go
CONFLICT (content): Merge conflict in pkg/cloudprovider/provider/vsphere/client.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 fix vSphere client not using the provided custom CA bundle
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release/v1.27

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