Don't configure cron from the pipeline

Configuring the Jenkins cron setup from the pipeline itself can be somewhat unexpected. The pipeline should be method not policy.

This is in particular confusion/harmful at the moment as a common workflow for bigger work or tests on Jenkinsfile is to create a new branch for the work and setup a playground jenkins job. Due to the pipeline setting the policy this job will then also run every night rather then on demand.

Signed-off-by: Sjoerd Simons sjoerd.simons@collabora.co.uk