Commit ed5aa85f37
qemu: don't use chardev FD passing for vhostuser backend
altered the legacy DO_TEST macro.
Run the test against capabilities of QEMU 2.5.0 (which did not
support QEMU_CAPS_CHARDEV_FD_PASS) as well as the latest version.
Signed-off-by: Ján Tomko <jtomko@redhat.com>