Drop maxage default to 7 days (from 14)
    
    Now we want to test Rawhide, 14 days is a bit too long. After
    13 days, Rawhide updates are absolutely piling up, and it can
    cause the `dnf update` run at the start of update tests to time
    out.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>