Re-enable memory_check test (on Everything, with WS packages)
    
    We were only running this test on the Workstation boot ISO...
    then that was removed, and so we actually never ran this test at
    all any more. We should run it on at least one image as check-
    compose uses the output to check whether installer memory usage
    has increased. I initially ran it on Workstation as that installs
    the most packages; so let's run it on Everything but use the
    Workstation package set.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>