[maven-release-plugin] prepare release mesos-0.12.0-beta-1
[maven-release-plugin] prepare release mesos-0.12.0-beta-1

jenkinsci/mesos-plugin,vinodkone/mesos-plugin,vinodkone/mesos-plugin,maselvaraj/mesos-plugin,mesosphere/mesos-plugin,jenkinsci/mesos-plugin,mesosphere/mesos-plugin,jenkinsci/mesos-plugin,maselvaraj/mesos-plugin