Omit the multipart hash if Workhorse S3 client is used

The Workhorse S3 client handles multipart uploads in a much more robust
way. We don't need to generate pre-signed URLs when it is used.

lib/object_storage/direct_upload.rb

@@ -206,7 +206,7 @@ module ObjectStorage
     end
 
     def requires_multipart_upload?
-      config.aws? && !has_length && can_use_multipart_upload?
+      config.aws? && !has_length && can_use_multipart_upload? && !use_workhorse_s3_client?
     end
 
     def can_use_multipart_upload?

spec/lib/object_storage/direct_upload_spec.rb

@@ -162,6 +162,10 @@ RSpec.describe ObjectStorage::DirectUpload do
         it 'enables the Workhorse client' do
           expect(subject[:UseWorkhorseClient]).to be true
         end
+
+        it 'omits the multipart upload URLs' do
+          expect(subject).not_to include(:MultipartUpload)
+        end
       end
 
       context 'when only server side encryption is used' do