janssonrpc-c: Fix double free if retry timer add fails

- Fix double free if schedule_retry fails when adding
  request retry timer. timeout_cb called fail_request
  which frees req after schedule_retry had already
  done so.

(cherry picked from commit bce9cf9)

modules/janssonrpc-c/janssonrpc_request.c

@@ -253,8 +253,6 @@ int schedule_retry(jsonrpc_request_t* req)
 
 	new_req->ntries = req->ntries;
 
-	free_request(req);
-
 	const struct timeval tv = ms_to_tv(time);
 
 	new_req->retry_ev = evtimer_new(global_ev_base, retry_cb, (void*)new_req);
@@ -264,6 +262,8 @@ int schedule_retry(jsonrpc_request_t* req)
 		goto error;
 	}
 
+	free_request(req);
+
 	return 0;
 error:
 	ERR("schedule_retry failed.\n");