Author: David Monllao
MDL-41342 admin: Adding warning when upgrading a test site
http://git.moodle.org/gw?p=moodle.git;a=commit;h=6e09cf98fa824a17dffef96f6efa8dd07b633e12
http://github.com/moodle/moodle/commit/6e09cf98fa824a17dffef96f6efa8dd07b633e12
+ 2.6 en [testsiteupgradewarning,core_admin]