Stop savepoint call overwriting core moodle version!

This is overwriting core moodles save point!

So say you're on Moodle 2.7 with a version of: 2014051202.07
local_mobile comes along and sets it to 2014060300.

This now means that if I upgrade moodle to something else, all the upgrade steps between 20140512 and 20140603 will be skipped, as it believes its already on that version!