Code review comment for lp:~al-maisan/launchpad/ejdt-n-1

Hello there!

This branch integrates all the logic that was put in place beforehand to
facilitate the estimation of build farm job dispatch times.

The main functions _estimateTimeToNextBuilder() and _estimateJobDelay()
were streamlined so that they do only thing namely estimate the
time/delay in seconds

  - until the next builder capable of running the job of interest (JOI)
    becomes available and
  - until all the jobs ahead of the JOI have been dispatched

The bulk of this branch (roughly two thirds) is concerned with cleaning
up tests and although it has gotten a bit bigger than I wanted it's
still fairly "review-able" :)

Tests to run:

   bin/test -vv -t test_buildqueue

No "make lint" errors or warnings.