Fix CPU Credit issues on Micro instances

Warning - Requires reboot!

On Ubuntu linux < 4.8.0-27.29 there's a bug that causes `kswapd` to get locked, consuming CPU and eating up your CPU Credits, resulting in your server running slowly as it's always out of credits even when idle. If find your CPU utilization is always above 10% even when you know the server is idle, and your CPU credit is continually bouncing around 0-0.03, you probably have this issue.

See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518457