Force GNOME to notify updates, re-enable test on Workstation
    
    Summary:
    GNOME's update notification criteria are pretty braindead: it
    fires the update check timer once on login then once every hour
    thereafter, but only actually checks for and notifies of updates
    once a day if it's after 6am(?!?!?!). So we have to do a bunch
    of fiddling around to ensure we reliably get a notification.
    Move the clock to 6am if it's earlier than that, and reset the
    'last update check' timer to 48 hours ago, then log in to GNOME
    after that.
    
    Note: I thought this still wasn't fully reliable, but I've looked
    into all the recent failures of either test on staging and
    there's only one which was really 'no update notification came
    up', and the logs clearly indicate PK did run an update check,
    so I don't think that was a test bug (I think something went
    wrong with the update check). The other failures are all 'GNOME
    did something wacky', plus one case where the needle didn't quite
    match because I think the match area is slightly too tall; I'll
    fix that in a second.
    
    Test Plan:
    Run the tests on both KDE and GNOME and check they
    work properly now (assuming nothing unrelated breaks, like KDE
    crashing...)
    
    Reviewers: jskladan, garretraziel
    
    Reviewed By: garretraziel
    
    Subscribers: tflink
    
    Differential Revision: https://phab.qadevel.cloud.fedoraproject.org/D1039