This patch adds the java_home variable to all supported
operating systemd, and gives the user the option to
set it themselves. It also updates config.pp to
ensure that the JAVA_HOME variable is set to
the desired java_home.
In some cases it can cause problems and report these kind of errors:
$ update-java-alternatives -s /usr/lib/jvm/java-1.7.0-openjdk-amd64 --jre
update-alternatives: error: no alternatives for policytool
update-alternatives: error: no alternatives for policytool
