Take a look at implementing lazy evaluation for job xml

[ghale]

Right now each job evaluates dsl and xml blocks and immediately serializes to xml during the configuration phase. We should look at lazy evaluating the xml sometime after the configuration phase but before the first update occurs. That is, we don't want to uncover a syntax error in the configuration of job 3 after jobs 1 and 2 have already been updated. We also need to be careful about evaluating more than once as some of the jenkins-job-dsl commands will add multiple xml nodes.