use buildd variant when creating new cowbuilder environments
use buildd variant when creating new cowbuilder environments

Thanks to Thorsten Glaser for the idea.

vorlock/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,n054/jenkins-debian-glue,mika/jenkins-debian-glue,bmiklautz/jenkins-debian-glue,webtrekk-kane/jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,hetznerZA/jenkins-debian-glue,wikimedia/operations-debs-jenkins-debian-glue,hetznerZA/jenkins-debian-glue,kartikm/jenkins-debian-glue,linuxmaniac/jenkins-debian-glue,mika/jenkins-debian-glue,kartikm/jenkins-debian-glue,tanglu-org/jenkins-tanglu-buildkit,bmiklautz/jenkins-debian-glue,jbfavre/jenkins-debian-glue,tanglu-org/jenkins-tanglu-buildkit,webtrekk-kane/jenkins-debian-glue,jbfavre/jenkins-debian-glue,hashar/jenkins-debian-glue,cclausen/jenkins-debian-glue,tonin/jenkins-debian-glue,zeha/jenkins-debian-glue,tanglu-org/jenkins-tanglu-buildkit,hashar/jenkins-debian-glue,cclausen/jenkins-debian-glue,n054/jenkins-debian-glue,tonin/jenkins-debian-glue,zeha/jenkins-debian-glue,vorlock/jenkins-debian-glue