Include PID in exception logs

lib/cluster.js

@@ -131,7 +131,8 @@ function start(service) {
 process.on("uncaughtException", function(err) {
   logger.error({
     message: "Uncaught exception in master process, exiting",
-    exception: err
+    exception: err,
+    pid: process.pid
   });
   cluster.removeListener("exit", restartWorker);
   for (let pid in cluster.workers)