[Build] suppress curl/wget progress bars

In the Jenkins console output, `curl` gives us mountains of `#` symbols as it tries to show its download progress.

![noise from curl in Jenkins output](http://i.imgur.com/P2E7yUw.png)

I don't think this is useful so I've changed things to suppress these progress bars. If there is actually some use to this, feel free to reject this proposal.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #2279 from nchammas/trim-test-output and squashes the following commits:

14a720c [Nicholas Chammas] suppress curl/wget progress bars