Add a fail_on_dirty_source utility method

We'll use this in both jenkins.rake and jenkins_dynamic.rake.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Pull library requirement out into a utility method

We require and fail with a message all over the place, so let's abstract into a
utility method.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Add job triggering to jenkins_dynamic.rake

Previously, jenkins dynamic could create the jobs, but not trigger them. This
commit updates the dynamic job creation to also trigger the execution of the
job first job after it has been created. Unfortunately, this uses a lot of the
same logic that jenkins.rake does. Ideally we would be able to get rid of all
of this duplication, and we will. Just not right now.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>