Merge pull request #66261 from vmware/fix-locate-resource-pool

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Fix locating resourcepool-path specified in the vsphere.conf file

**What this PR does / why we need it**:
When volume is provisioned using the vsphere storage policy, `resourcepool-path` specified in the `vsphere.conf` file is used for creating a shadow/dummy VM.  Dummy VM is temporarily created and then deleted once volume is created on the compatible Datastore.

At present If user specifies `resourcepool-path` in the `vsphere.conf` file,  volume provisioner is not able to locate the compute resource for the given path. This is because look up is made using `finder.DefaultComputeResource(ctx)` and `finder.ComputeResource(ctx, computePath)`, which is not correct. If user specifies name of the cluster or cluster path then provisioning works.

This is resolved with using correct govmomi method - `func (f *Finder) ResourcePoolOrDefault(ctx context.Context, path string) (*object.ResourcePool, error)`


**Which issue(s) this PR fixes**
Fixes # https://github.com/vmware/kubernetes/issues/493

**Special notes for your reviewer**:
Following testing is performed for this change.

1) specified resource-pool path in the `vsphere.conf` file and verified VM is created under the specified resource pool.

```
resourcepool-path="ClusterFolder-1/cluster-vsan-1/Resources/ShadowVMPool"
```

2) If resource pool is not available, specified cluster's default resource pool path in the `vsphere.conf` file and verified volume provisioning works. For this case, VM is directly created under cluster.

```
resourcepool-path="ClusterFolder-1/cluster-vsan-1/Resources"
```

3) Verified above with having multiple clusters with the same name in one datacenter.
4) Verified with empty resource pool path in the vsphere.conf file. 

```
resourcepool-path=""
```
As expected, provisioning is failing with `Failed to provision volume with StorageClass "vsan-gold-policy": no default resource pool found`.

Refer to this datacenter inventory for the path specified in the `resourcepool-path` configuration.

![image](https://user-images.githubusercontent.com/22985595/42792922-738e3f9c-892c-11e8-9e51-32e2328b116b.png)

Current documentation describes `resourcepool-path`configuration is optional, which needs to be corrected once PR is merged. For policy based provisioning this is not an optional parameter.

Documentation link: https://vmware.github.io/vsphere-storage-for-kubernetes/documentation/existing.html



**Release note**:

```release-note
Fix for resourcepool-path configuration in the vsphere.conf file.
```

cc: @kubernetes/vmware

pkg/cloudprovider/providers/vsphere/vclib/datacenter.go

@@ -155,20 +155,16 @@ func (dc *Datacenter) GetDatastoreByName(ctx context.Context, name string) (*Dat
 }
 
 // GetResourcePool gets the resource pool for the given path
-func (dc *Datacenter) GetResourcePool(ctx context.Context, computePath string) (*object.ResourcePool, error) {
+func (dc *Datacenter) GetResourcePool(ctx context.Context, resourcePoolPath string) (*object.ResourcePool, error) {
 	finder := getFinder(dc)
-	var computeResource *object.ComputeResource
+	var resourcePool *object.ResourcePool
 	var err error
-	if computePath == "" {
-		computeResource, err = finder.DefaultComputeResource(ctx)
-	} else {
-		computeResource, err = finder.ComputeResource(ctx, computePath)
-	}
+	resourcePool, err = finder.ResourcePoolOrDefault(ctx, resourcePoolPath)
 	if err != nil {
-		glog.Errorf("Failed to get the ResourcePool for computePath '%s'. err: %+v", computePath, err)
+		glog.Errorf("Failed to get the ResourcePool for path '%s'. err: %+v", resourcePoolPath, err)
 		return nil, err
 	}
-	return computeResource.ResourcePool(ctx)
+	return resourcePool, nil
 }
 
 // GetFolderByPath gets the Folder Object from the given folder path