desktop_update_graphical: try to workaround GGO #2442
In current F40 and Rawhide, this test is frequently failing
because gnome-software is behaving weirdly at startup - the
third-party software dialog moves around even more than before,
the app seems to get stuck in the "not responding" state
briefly sometimes, and there's a very weird state it gets into
sometimes where the window is shorter than usual and clicks
don't seem to register in the right place. While I'm trying to
bisect these bugs, these magic voodoo incantations (tested on
the staging instance) seem to mostly work around the weird
behaviour, and setting RETRY=2 should backstop it a bit further.
Signed-off-by: Adam Williamson <awilliam@redhat.com>