Persisting filecache causing persistence issues

[krokicki]

The filecache directory is in the user directory by default, and when we turned on AppStream user setting persistence, it tried to save all the cached files to S3. However the profile persistence has a max of 1GB, and they get corrupted when they are overfilled. We need to stop the filecache from persisting, and test to make sure user settings are persisted even after browsing many samples that fill up the file cache.