When using the prermalink from sections to make internal links, it doesnt get recalculated on import or course restore.

How to recpreduce the bug.

1. Make a new course with four sections
2. Rename the sections and insert some random activities.
3. Go to editmode and edit a section
4. Click on "Permalink"
5. Copy the permalink
6. Go to the top section and insert a "Text and media area"
7. Click on link icon, insert some link tekst and past in the copied permalink
8. Save
9. Go to the front of the course to see the link is working.
10. Click on "More" in the course menu and choose "Course reuse"
11. Make a backup of the course
12. Restore the course
13. Go to the cours page and click on the link

Expected behavior. 

That the permalink is recalculated and takes you to the right course section

What actually happens. 

The link does nothing.

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What happens is that the course id is recalculated, but the section id isnt.