In https://gitlab.com/gitlab-org/gitlab/merge_requests/16926 we added
gRPC timeouts for calls that did not previously have timeouts to prevent
Sidekiq queries from getting stuck. In addition, we also made long
timeouts 55 seconds for non-Sidekiq requests, but this meant Rake tasks
also fell into this bucket. Rake backup tasks with large repositories
would fail because the CreateBundle RPC would time out after 55 seconds.

To avoid this trap, we flip the logic of long_timeout: instead of
checking for Sidekiq (or other background jobs), we only lower the
timeout to 55 seconds if we're servicing a Web request in Puma or
Unicorn.

Closes https://gitlab.com/gitlab-org/gitlab/issues/22398