Spec failure due to Gitaly GPRC::Unavailable: Failed parsing HTTP/2

See https://gitlab.com/gitlab-org/gitlab-ce/builds/15840810

 ActionView::Template::Error:
       14:Failed parsing HTTP/2
     # ./lib/gitlab/git/repository.rb:1270:in `rescue in gitaly_migrate'
     # ./lib/gitlab/git/repository.rb:1266:in `gitaly_migrate'
     # ./lib/gitlab/git/repository.rb:48:in `root_ref'
     # ./app/models/repository.rb:465:in `root_ref'
     # ./app/models/repository.rb:51:in `block (2 levels) in cache_method'
     # ./lib/repository_cache.rb:20:in `fetch'
     # ./app/models/repository.rb:1071:in `cache_method_output'
     # ./app/models/repository.rb:51:in `block in cache_method'
     # ./app/helpers/gitlab_routing_helper.rb:34:in `project_files_path'