Sitedata cleaner update all files matching found mimetype, instead of only selected context level

[weilai-irl]

In the sitedata cleaner, the current logic uses the selected context level to find all the mime types to delete, but when updating matching mdl_files records, it ignores context level, and instead updates all records matching the mime types, regardless of context level and component etc.

I have developed a solution and will create a PR.

Regards,
Lai