Timeout is not set for gitaly fetch_remote calls

In Gitlab::Shell we don't currently pass a timeout to Gitlab::GitalyClient::RepositoryService#fetch_remote. On the route with gitaly disabled this timeout is equal to Gitlab.config.gitlab_shell.git_timeout, which defaults to 3 minutes, which is a great difference with the default for Gitaly::FetchRemoteRequest, which is zero. This is especially troublesome for geo.