MDL-72275 timeline: Add default offset to template

This value was being passed in the template, but the template
had 0 hardcoded instead of injecting the context value. With the other
bug fixes in this issue correctly loading the "All" view properly on
page load, this uncovered that at load time, the course view would not
load overdue items, which also meant a behat test was failing.

blocks/timeline/templates/view.mustache

@@ -58,7 +58,7 @@
             data-limit="2"
             data-offset="0"
             data-days-limit="{{dayslimit}}"
-            data-days-offset="0"
+            data-days-offset="{{daysoffset}}"
             data-no-events-url="{{urls.noevents}}"
             id="view_courses_{{uniqid}}"
         >