tests: libxl: skip tests with nested_hvm

Commit 95d19cd0 unconditionally adjusted the tests to account for
the conditional move of the nested_hvm setting location.

Run the affected tests only for the new setup (witnessed by
LIBXL_HAVE_BUILDINFO_NESTED_HVM).
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

tests/libxlxml2domconfigtest.c

@@ -207,9 +207,13 @@ mymain(void)
     DO_TEST("cpu-shares-hvm");
     DO_TEST("variable-clock-hvm");
     DO_TEST("moredevs-hvm");
-    DO_TEST("vnuma-hvm");
     DO_TEST("multiple-ip");
+
+# ifdef LIBXL_HAVE_BUILDINFO_NESTED_HVM
+    DO_TEST("vnuma-hvm");
     DO_TEST("fullvirt-cpuid");
+# endif
+
 
     unlink("libxl-driver.log");