improve Multi-SCO completion handing in activity completion

Behat tests included for this change. Manual instructions for behat test: Add the multi-sco package to your course: https://github.com/danmarsden/moodle/blob/master_MDL-44712/mod/scorm/tests/packages/RuntimeMinimumCalls_SCORM12.zip Enable completion tracking at course level in the activity completion rules set: Show activity as complete when conditions are met Tick "completed" checkbox make sure require all scos to return completion status is unticked. Enter scorm as student - view main page of SCORM - don't navigate through package at all, just hit "exit activity" Check to make sure activity completion shows as "complete" for that user. Create new package as above, but this time set "Require all scos to return completion status" to yes (ticked) Enter scorm as student - view main page - don't navigate through package at all, just hit "exit activity" Check to make sure activity completion shows as NOT "complete" for that user. Re-enter SCORM and progress through each SCO - (click on each sco name in TOC on left) - you do not need to complete any quizzes - just "view" each sco. - when every sco has been viewed (green tick appears beside the name of the sco in the tree) hit the exit activity link at top right. Check to make sure activity completion shows as "complete" for that user.