generate-svn-snapshot: always call svn upgrade
generate-svn-snapshot: always call svn upgrade

If the system has been upgraded in between, it might
fail with a missleading error message.

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