flatpak: Make sure we are refreshing the appstream metadata
Do the 6 hours trick in case the remote wasn't found at all.
Note for future self when testing the feature, a good way to force the refresh is by running:
$ sudo touch -d "2 weeks ago" /var/lib/flatpak/appstream/flathub/x86_64/.timestamp
BUG: 448521 FIXED-IN: 5.27
Edited by Nate Graham