Backports PR #10689
**Commit 1:**
build: always run build task in jenkins
We always run the build task now in jenkins jobs rather than only in the
core builds. This ensures that the build task runs in PR builds even
though the build artifacts are not used for anything.
Ideally all the selenium tests would run against this build rather than
it just being something that gets ran and forgotten about, but this is a
first step.
* Original sha: 9517d8ded4
* Authored by Court Ewing <court@epixa.com> on 2017-03-03T16:11:20Z
Until now, the ci setup tasks were stored in the Jenkins job configuration. This moves the setup into source control so that jenkins can be told to execute `./test/scripts/jenkins_{JOB_TYPE}.sh` no matter what branch of kibana it is dealing with.
