Fix to support Ubuntu Trusty Tahr.

Ubuntu 14.04 LTS comes with `update-alternatives` installed by default in `/usr/bin/`, instead of `/usr/sbin/` (which is where is it was in 12.04). This was causing the [puppet-jdk_oracle](http://github.com/tylerwalts/puppet-jdk_oracle) module to fail because it contained one hard-coded path for all Debian OSes. Added an extra case statement to allow for various possible locations of the `update-alternatives` tool, initially including just one known exception, i.e. Ubuntu 14.04 LTS.