tools/xl: fix possible uninitialized usage in printf_info()

printf_info_one_json() won't initialize the passed jso_r parameter on
error, and hence the usage in printf_info() needs prior initialization,
otherwise an uninitialized pointer is passed to json_object_put() on
failure.

Reported by the internal XenServer Coverity instance.

Fixes: f6c6f2679d ("libxl: Convert libxl__object_to_json() to json-c")
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

tools/xl/xl_info.c

@@ -154,7 +154,7 @@ void printf_info(enum output_format output_format,
 #ifdef HAVE_LIBJSONC
     int r;
     const char *buf;
-    json_object *jso;
+    json_object *jso = NULL;
 
     r = printf_info_one_json(&jso, domid, d_config);
     if (r)