Disable Transparent Huge Pages.
Test whether /sys/kernel/mm/transparent_hugepage/enabled exists.

(cherry picked from commit 8eeebe9b891a84017f1a65794598bbe890beeb59)
Signed-off-by: Reynold Xin <rxin@apache.org>
Merge pull request #70 from rxin/thp

Disable Transparent Huge Pages.