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Report InstanceID for vSphere Cloud Provider as UUID obtained from product_serial file 

**What this PR does / why we need it**:
vSphere Cloud Provider is not able to find the nodes for VMs created on vSphere v1.6.5. Kubelet fetches SystemUUID from file ```/sys/class/dmi/id/product_uuid```. vSphere Cloud Provider uses this uuid as VM identifier to get node information from vCenter. vCenter v1.6.5 doesn't recognize this uuids, as a result, nodes are not found. 

UUID present in file ```/sys/class/dmi/id/product_serial``` is recognized by vCenter. Yet,  Kubelet doesn't report this. Therefore, in this PR InstanceID is reported as UUID which is fetched from file 
```/sys/class/dmi/id/product_serial```.

**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 https://github.com/kubernetes/kubernetes/issues/58927

**Special notes for your reviewer**:
Internally review here: https://github.com/vmware/kubernetes/pull/452

Tested:
Launched K8s cluster using kubeadm (Used Ubuntu VM compatible with vSphere version 6.5.)
_**Note: Installed Ubuntu from ISO**_
Observed following:
```
Master
> cat /sys/class/dmi/id/product_uuid
743F0E42-84EA-A2F9-7736-6106BB5DBF6B

> cat /sys/class/dmi/id/product_serial
VMware-42 0e 3f 74 ea 84 f9 a2-77 36 61 06 bb 5d bf 6b

Node
> cat /sys/class/dmi/id/product_uuid
956E0E42-CC9D-3D89-9757-F27CEB539B76

> cat /sys/class/dmi/id/product_serial
VMware-42 0e 6e 95 9d cc 89 3d-97 57 f2 7c eb 53 9b 76
```
With this fix controller manager was able to find the nodes.
**controller manager logs**
```
{"log":"I0205 22:43:00.106416       1 nodemanager.go:183] Found node ubuntu-node as vm=VirtualMachine:vm-95 in vc=10.161.120.115 and datacenter=vcqaDC\n","stream":"stderr","time":"2018-02-05T22:43:00.421010375Z"}
```


**Release note**:

```release-note
vSphere Cloud Provider supports VMs provisioned on vSphere v1.6.5
```