Author: Ilya Tregubov
MDL-80599 core: Refactor enrol methods
Move update instance logic to its own method and cover with tests.
Also update enrol plugins to work woth new methods.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=56fb55683a0972cfd0f342ae0c038537f9104614
http://github.com/moodle/moodle/commit/56fb55683a0972cfd0f342ae0c038537f9104614
+ 4.4 en [plugindisabled,core_enrol]