Git commits in Moodle 3.9.x by Michael Aherne

commit 28a1f0943dac4176e1a17bb8521f671424fd883e
Author: Michael Aherne <michael.aherne@strath.ac.uk>
Date:   Mon, 17 Jun 2019 19:24:39 +0800
Tag:    v3.9.4

MDL-65941 cache: Prevent cache config failure on redis problems.