Increase timeout for Git-over-HTTP requests.

Fixes #2081 and https://gitlab.com/gitlab-org/gitlab-ce/issues/232.

Normal web requests are bound by the `Rack::Timeout` timeout of 60 seconds, while Grack Git-over-HTTP requests are only bound by Unicorn's timeout which is now set to 1 hour, which should be plenty.

The omnibus package should be updated to no longer use `unicorn['worker_timeout']` for the Unicorn timeout, but to set the `Slowpoke.timeout`.

See merge request !1619