qemucaps2xmltest: fix test to successfully run without kvm support
    
    Function virQEMUCapsInitGuestFromBinary detect kvm support by testing
    whether /dev/kvm exists or whether we pass path to kvmbin.  Provide the
    path we are testing via kvmbin for testing purpose instead of detecting
    presence of /dev/kvm to successfully run the tests on all hosts.
    
    Signed-off-by: Pavel Hrdina <phrdina@redhat.com>