CI: Avoid Flatpak triggers for tests
Remove Flatpak triggers, to speed up the tests (specifically on Fedora, they could even break the tests by a deadlock or something like that).
The bwrap claims on the Fedora had been due to flatpak runing its triggers, trying to do it in the bwrap. These triggers had been also causing those deadlocks or what it was (I do not what what precisely it is). The Debian image doesn't suffer of it, because they do not have any Flatpak triggers (yet). Unfortunately, the FLATPAK_TRIGGERSDIR evn variable did not work for me, thus I just delete the directory in question.
With respect of the first commit, The only commented line I'm not sure about is the dbus-daemon thing. Consult the comment above it. I only know this lets it work with no visible side effect.