adding topology support for zfspv (#7)

This PR adds support to allow the CSI driver to pick up a node matching the  topology specified in the storage class. Admin can specify allowedTopologies in the StorageClass to specify the nodes where the zfs pools are setup

```yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
allowVolumeExpansion: true
parameters:
  blocksize: "4k"
  compression: "on"
  dedup: "on"
  thinprovision: "yes"
  poolname: "zfspv-pool"
provisioner: zfs-localpv
volumeBindingMode: WaitForFirstConsumer
allowedTopologies:
- matchLabelExpressions:
  - key: kubernetes.io/hostname
    values:
      - gke-zfspv-pawan-default-pool-c8929518-cgd4
      - gke-zfspv-pawan-default-pool-c8929518-dxzc
```

Note: This PR picks up the first node from the list of nodes available.

Signed-off-by: Pawan <pawan@mayadata.io>

pkg/builder/build.go

@@ -136,6 +136,12 @@ func (b *Builder) WithThinProv(thinprov string) *Builder {
 	return b
 }
 
+// WithOwnerNode sets owner node for the ZFSVolume where the volume should be provisioned
+func (b *Builder) WithOwnerNode(host string) *Builder {
+	b.volume.Object.Spec.OwnerNodeID = host
+	return b
+}
+
 // WithBlockSize sets blocksize of ZFSVolume
 func (b *Builder) WithBlockSize(blockSize string) *Builder {
 	bs := "4k"