create droplet on kpack Image update

[#172542372]

Co-authored-by: Connor Braa <cbraa@pivotal.io>
Co-authored-by: Piyali Banerjee <pbanerjee@pivotal.io>

Author: cwlbraa

lib/cloud_controller/kpack/stager.rb

@@ -51,6 +51,7 @@ def mark_build_as_failed(build, message)
     end
 
     def update_image_resource(image, staging_details, builder_spec)
+      image.metadata.labels[DROPLET_GUID_LABEL_KEY.to_sym] = create_droplet_and_get_guid(staging_details)
       image.metadata.labels[BUILD_GUID_LABEL_KEY.to_sym] = staging_details.staging_guid
       image.spec.source.blob.url = blobstore_url_generator.package_download_url(staging_details.package)
       image.spec.build.env = get_environment_variables(staging_details)

spec/unit/lib/cloud_controller/kpack/stager_spec.rb

@@ -255,6 +255,7 @@ module Kpack
               labels: {
                 Stager::APP_GUID_LABEL_KEY => package.app.guid,
                 Stager::BUILD_GUID_LABEL_KEY => 'old-build-guid',
+                Stager::DROPLET_GUID_LABEL_KEY => 'old-droplet-guid',
                 Stager::STAGING_SOURCE_LABEL_KEY => 'STG',
               },
               annotations: {
@@ -291,6 +292,7 @@ module Kpack
         it 'updates the existing Image resource' do
           updated_image = Kubeclient::Resource.new(existing_image.to_hash)
           updated_image.metadata.labels[Kpack::Stager::BUILD_GUID_LABEL_KEY.to_sym] = build.guid
+          updated_image.metadata.labels[Kpack::Stager::DROPLET_GUID_LABEL_KEY.to_sym] = droplet.guid
           updated_image.spec.source.blob.url = 'package-download-url'
           updated_image.spec.build.env = [
             { name: 'FOO', value: 'BAR' }