tests: don't test json when not compiled in

Now that the segfault is solved, we can skip instead of fail
the test when yajl is not present.

* tests/qemumonitorjsontest.c (mymain): Skip if no yajl.

tests/qemumonitorjsontest.c

 /*
- * Copyright (C) 2011-2012 Red Hat, Inc.
+ * Copyright (C) 2011-2013 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -444,6 +444,11 @@ mymain(void)
     int ret = 0;
     virCapsPtr caps;
 
+#if !WITH_YAJL
+    fprintf(stderr, "libvirt not compiled with yajl, skipping");
+    return EXIT_AM_SKIP;
+#endif
+
     if (virThreadInitialize() < 0)
         exit(EXIT_FAILURE);