Simplify os::hostname() in libstout.
Hadoop changes; see below.

    - Added CDH4.2.0 support to TUTORIAL.sh
    - Use .tar.xz for Hadoop dist (LZMA)
    - Fixed Hadoop dist extraction in launcher
    - Add pre/post packaging hooks to TUTORIAL.sh
    - Don't run the jobtracker at the end by default
Fix for deadlock in Hadoop MesosScheduler.

This resolves JIRA issue MESOS-429.