Spawn cinder volumes in the same Availability Zone

At the moment volumes for workers are gonna be spawn in a random
AZ completely disregarding user request for Availability Zone.

In a design where cross_az_attach is not posisble an attempt
to add a volume to worker has high failure percentage due to random
selection of AZ.

This patch suggests using provided to cluster availability_zone by
supplying `availability` parameter to cinder csi [1]

This ensures that volume will be created in a same zone as workers are
preventing failures where cross_az_attach is False.

[1] https://github.com/kubernetes/cloud-provider-openstack/blob/master/docs/cinder-csi-plugin/using-cinder-csi-plugin.md#supported-parameters

magnum_cluster_api/resources.py

@@ -333,6 +333,9 @@ def get_object(self) -> pykube.ConfigMap:
                             "provisioner": "cinder.csi.openstack.org",
                             "parameters": {
                                 "type": vt.name,
+                                "availability": self.cluster.labels.get(
+                                    "availability_zone", ""
+                                ),
                             },
                             "reclaimPolicy": "Delete",
                             "volumeBindingMode": "Immediate",