Git commits in Moodle 3.3.x by Fred Woolard

commit 58235c3774e3d37870a64e974c1313d83cf50816
Author: Fred Woolard <woolardfa@appstate.edu>
Date:   Tue, 24 Oct 2017 01:22:42 +0800
Tag:    v3.3.3

MDL-57477 core: If memcached 3.x mimic 2.2.0 lock acquisition behavior