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

@@ -101,10 +101,13 @@ cluster._getServer = function(obj, options, cb) {
     if (typeof obj._setServerData === 'function')
       obj._setServerData(reply.data);
 
-    if (handle)
-      shared(reply, handle, indexesKey, index, cb);  // Shared listen socket.
-    else
-      rr(reply, indexesKey, index, cb);              // Round-robin.
+    if (handle) {
+      // Shared listen socket
+      shared(reply, { handle, indexesKey, index }, cb);
+    } else {
+      // Round-robin.
+      rr(reply, { indexesKey, index }, cb);
+    }
   });
 
   obj.once('listening', () => {
@@ -129,7 +132,7 @@ 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 +149,8 @@ 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);