property 'RESKEY:availability_zones' for volume types ignored by volume creation

[Robbert Nijgh]

Background example:
In this example I have 3 cinder availability zones(AZs): storage01, storage02 & storage03
I have 2 volume types: Ceph & NetApp

The volume type Ceph is available in all 3 AZs, however NetApp is only available in storage02 and storage03.

With the OpenStack CLI it is possible to set which AZs a volume type is available in:
> openstack volume type set NetApp --availability-zone storage02,storage03
> openstack volume type show NetApp
+--------------------+-------------------------------------------------------------------------------+
| Field | Value |
+--------------------+-------------------------------------------------------------------------------+
| access_project_ids | b1593bc2d19e4b94ae815eec6f569d87 |
| description | |
| id | 575c147c-1a64-4674-bd8d-da8c98be9dba |
| is_public | False |
| name | NetApp |
| properties | RESKEY:availability_zones='storage02,storage03', volume_backend_name='netapp' |
| qos_specs_id | 120f04a0-65dd-4cce-aeaa-14abf7e30f05 |
+--------------------+-------------------------------------------------------------------------------+

Bug // missing feature:
When clicking 'CREATE VOLUME', you're shown the fill-in/select form for the creation of a volume(s). When the volume-type Ceph is selected, it shows all available AZs in the select-able Availablity Zone list.

However, when NetApp is selected, it also shows all available AZs in the Availability Zone list. When a client/end-user selects this volume-type with the storage01 AZ (which is not available in the volume type property). It results in a ugly Error message, stating the AZ 'storage01' is invalid.

Expected result:
When a volume-type that has the property 'RESKEY:availability_zones' configured, is selected. It is expected for horizon to dynamically change the list of Availability zones in the volume create Form. So that clients/end-users arent able to see or select a AZ that does not have the volume-type.