apps_startstop: don't rollback, defend against KDE mistypes
    
    This comes from trying to fix the annoying recurring problem with
    mistypes in KDE which has been going on since at least December.
    First, we add the attempt to kind of 'precache' the kicker menu
    in aasetting.pm. Then, I thought, all this snapshot loading has
    to be putting a lot of load on the workers. And when each subtest
    passes, it shouldn't really be necessary - they all end with
    quit_with_shortcut(), which verifies that the app exited and we
    got back to a blank desktop, so successful subtests should not
    usually interfere with each other. We probably only want to
    rollback on *failed* subtests, which is in fact openQA's default
    behavior. There only seems to be one case where a test changes the
    system state such that later tests might be affected, so I kept
    always_rollback just for that one. I've run this through three
    cycles on GNOME and KDE and it looks good.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>