install jq on Jenkins agents and upgrade to recent docker

[ixdy]

The lack of jq on Jenkins keeps tripping me up, and it's a prerequisite for anago, so we should probably just install it on the agent image.

We're also still using an ancient version of docker (1.9.1, from November 2015), which has started causing problems.

We had issues with 1.10, which is why we originally held to 1.9.1.
Recent versions of docker have been more stable, though, so it'd probably be safe to upgrade, at least to the version used on COS (1.11.2).

[ixdy]

cc @fejta @david-mcmahon

[ixdy]

/assign

This is apparently a lot easier than I first realized.

I'm also gonna bump go to 1.8.3, though I'm not sure anything uses the version on Jenkins anymore.