Git commits in Moodle 3.4.1 by Carlos Alexandre S. da Fonseca

commit fdddb80b708d10c00de3362bebc2f9559f694590
Author: Carlos Alexandre S. da Fonseca <bozohhot@hotmail.com>
Date:   Tue, 21 Nov 2017 20:28:13 +0800
Tag:    v3.4.1

MDL-24678 mod_chat: Fixed race condition on chat module