tests: Don't use testutils in mock libraries
    
    Mock libraries are not built with testutils.c, but there's one which
    uses VIR_TEST_DEBUG.  But because that debug should be an error, if we
    change it, then it will not only be more semantically correct, but mingw
    compiler will be happier as well.
    
    It also follows suit with all other mock libraries.
    
    For few other things, used in this file, need libvirt.la to be added
    into LIBADD for mingw as well.
    
    Signed-off-by: Martin Kletzander <mkletzan@redhat.com>