Bump Dependency on openjdk-6-jre-headless to openjdk-7-jre-headless
Bump Dependency on openjdk-6-jre-headless to openjdk-7-jre-headless

Make lintian happy:
| E: jenkins-debian-glue-buildenv-slave: depends-on-obsolete-package depends: openjdk-6-jre-headless

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