We don't keep duration for jobs
We don't keep duration for jobs

We always just return finished at and started at for jobs, so just let
travis always calculate duration from those fields.

Tiger66639/travis-web,fotinakis/travis-web,mjlambert/travis-web,travis-ci/travis-web,fotinakis/travis-web,2947721120/travis-web,travis-ci/travis-web,jlrigau/travis-web,Tiger66639/travis-web,jlrigau/travis-web,mjlambert/travis-web,2947721120/travis-web,Tiger66639/travis-web,travis-ci/travis-web,Tiger66639/travis-web,fauxton/travis-web,fauxton/travis-web,mjlambert/travis-web,travis-ci/travis-web,fotinakis/travis-web,fauxton/travis-web,fauxton/travis-web,jlrigau/travis-web,jlrigau/travis-web,mjlambert/travis-web,fotinakis/travis-web,2947721120/travis-web,2947721120/travis-web