Fix PoolCluster _findCaches to be plain object

Author: dougwilson

lib/PoolCluster.js

@@ -144,8 +144,12 @@ PoolCluster.prototype.getConnection = function(pattern, selector, cb) {
   namespace.getConnection(cb);
 };
 
+PoolCluster.prototype._clearFindCaches = function _clearFindCaches() {
+  this._findCaches = Object.create(null);
+};
+
 PoolCluster.prototype._findNodeIds = function(pattern) {
-  if (typeof this._findCaches[pattern] !== 'undefined') {
+  if (this._findCaches[pattern] !== undefined) {
     return this._findCaches[pattern];
   }
 
@@ -214,10 +218,6 @@ PoolCluster.prototype._getConnection = function(node, cb) {
   });
 };
 
-PoolCluster.prototype._clearFindCaches = function() {
-  this._findCaches = {};
-};
-
 /**
  * PoolNamespace
  */