Author: Damyon Wiese
MDL-45412 Cache: Mongo DB string change (older is less than)
http://git.moodle.org/gw?p=moodle.git;a=commit;h=e4f1dd46b0f74bb1f6fbc38d5aa60c0304cd7018
http://github.com/moodle/moodle/commit/e4f1dd46b0f74bb1f6fbc38d5aa60c0304cd7018
+ 2.7 en [pleaseupgrademongo,cachestore_mongodb]