fdo#72774: Ensure that all the group fields are in cache upon file load.

This resolves the originally reported issue in that bug (in Comment 1).

Change-Id: I6fb85cff1eafb78d784605aa08e7d992a1ac36e0
fdo#72774: Add test for group field cache population on file load.

Change-Id: Iddde39da57db0d6be9f066f3e2bdb0526932edc6