Reduce QEMURAM back to 3G for most cases
    
    Hopefully https://bugzilla.redhat.com/show_bug.cgi?id=2133829
    is fully resolved/worked around by now, and we shouldn't need
    these any more. We could drop back to 2G but let's just do
    3G for now.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>