Add option to disable THP to RPM

Many Linux users of Couchbase server run into problems due to having Transparent Huge Pages (THP) enabled in their OS. Although we strongly recommend disabling this, it's often overlooked. It would be good to include a post install script to the RPM/DEB package that prompted the user asking if they would like the Couchbase installer to disable THP across the system, then we disable it and possibly recommend a reboot. This is not dissimilar to what we do on Windows and TCP port settings.