MDL-47572 libraries: modify unittest to avoid random timing fail

Thanks to Nigel Cunningham
MDL-47583 tinymce_managefiles: correctly decode filename
Merge branch 'wip-MDL-47583-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE
Merge branch 'wip-MDL-47572-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE