Interpolate cloud_properties before passing to CPI update_disk

Both update_detached_disks and update_disk_cpi were passing raw
cloud_properties to the CPI, which could contain unresolved variable
placeholders like ((...)).  The create_disk path already resolves
these via variables_interpolator.interpolate_with_versioning; do the
same for the update paths.

Author: neddp

src/bosh-director/lib/bosh/director/disk_manager.rb

@@ -84,8 +84,12 @@ def update_detached_disks(instance_plan)
 
         begin
           cloud = cloud_for_cpi(active_vm.cpi)
+          resolved_cloud_properties = @variables_interpolator.interpolate_with_versioning(
+            new_disk.cloud_properties,
+            instance_plan.instance.desired_variable_set,
+          )
           @logger.info("Updating detached disk '#{old_disk_model.disk_cid}' via CPI")
-          new_disk_cid = cloud.update_disk(old_disk_model.disk_cid, new_disk.size, new_disk.cloud_properties)
+          new_disk_cid = cloud.update_disk(old_disk_model.disk_cid, new_disk.size, resolved_cloud_properties)
 
           updates = { size: new_disk.size, cloud_properties: new_disk.cloud_properties }
           if new_disk_cid && new_disk_cid != old_disk_model.disk_cid
@@ -316,7 +320,11 @@ def update_disk_cpi(instance_plan, new_disk, old_disk)
 
       begin
         cloud = cloud_for_cpi(old_disk_model.instance.active_vm.cpi)
-        new_disk_cid = cloud.update_disk(old_disk_model.disk_cid, new_disk.size, new_disk.cloud_properties)
+        resolved_cloud_properties = @variables_interpolator.interpolate_with_versioning(
+          new_disk.cloud_properties,
+          instance_plan.instance.desired_variable_set,
+        )
+        new_disk_cid = cloud.update_disk(old_disk_model.disk_cid, new_disk.size, resolved_cloud_properties)
       rescue Bosh::Clouds::NotImplemented, Bosh::Clouds::NotSupported => e
         @logger.info("IaaS native update not possible for disk #{old_disk_model.disk_cid}. Falling back to creating new disk.\n#{e.message}")
         attach_disk(old_disk_model, instance_plan.tags)

src/bosh-director/spec/unit/bosh/director/disk_manager_spec.rb

@@ -178,6 +178,12 @@ module Bosh::Director
           { 'new' => 'properties' }
         end
 
+        before do
+          allow(variables_interpolator).to receive(:interpolate_with_versioning)
+            .with(anything, anything)
+            .and_return(cloud_properties)
+        end
+
         context 'when disk size and properties change' do
           it 'updates the disk via cpi' do
             disk_manager.update_persistent_disk(instance_plan)
@@ -806,6 +812,9 @@ module Bosh::Director
       before do
         allow(cloud_factory).to receive(:get).with('my-cpi', nil).and_return(cloud)
         allow(cloud_factory).to receive(:get).with('my-cpi').and_return(cloud)
+        allow(variables_interpolator).to receive(:interpolate_with_versioning)
+          .with(anything, anything)
+          .and_return(cloud_properties)
       end
 
       let(:enable_cpi_update_disk) { true }