Git commits in Moodle 2.6.2 by Mark Nielsen

commit 91e6e560147c9c511a193c5fd06a2a7a7c4a1a34
Author: Mark Nielsen <mark@moodlerooms.com>
Date:   Fri, 17 Jan 2014 03:22:28 +0800
Tag:    v2.6.2

MDL-43734: Prevent purging of all user session cache