Add job runtime stats

Use state change times to determine job start and end times for a
run, and log runtime stats for the job, job+branch, job+branch+image,
job+branch+image+provider, as well as build counts for each of those.

Update the fake yaml file to align the ZMQ port with the fake servers.

Add statsd to the fake servers.

Add instructions on how to run a fake nodepool that emits statsd info.

Change-Id: I5296cafd191f363698a088fd50d5da24902fd104
Merge "Add job runtime stats"