cluster: restructure to same prototype for cluster child

Since `rr` and `shared` both belongs to the same prototype declaration
and differes only in the handler declaration, this can be abstracted to
a same type of function arguments passing.

Author: yashLadha

lib/internal/cluster/child.js

@@ -102,9 +102,9 @@ cluster._getServer = function(obj, options, cb) {
       obj._setServerData(reply.data);
 
     if (handle)
-      shared(reply, handle, indexesKey, index, cb);  // Shared listen socket.
+      shared(reply, { handle, indexesKey, index }, cb); // Shared listen socket.
     else
-      rr(reply, indexesKey, index, cb);              // Round-robin.
+      rr(reply, { indexesKey, index }, cb);             // Round-robin.
   });
 
   obj.once('listening', () => {
@@ -129,7 +129,7 @@ function removeIndexesKey(indexesKey, index) {
 }
 
 // Shared listen socket.
-function shared(message, handle, indexesKey, index, cb) {
+function shared(message, { handle, indexesKey, index }, cb) {
   const key = message.key;
   // Monkey-patch the close() method so we can keep track of when it's
   // closed. Avoids resource leaks when the handle is short-lived.
@@ -146,8 +146,8 @@ function shared(message, handle, indexesKey, index, cb) {
   cb(message.errno, handle);
 }
 
-// Round-robin. Primary distributes handles across workers.
-function rr(message, indexesKey, index, cb) {
+// Round-robin. Master distributes handles across workers.
+function rr(message, { indexesKey, index }, cb) {
   if (message.errno)
     return cb(message.errno, null);