chore($cache): do not add entry to LRU hash when value is undefined

When adding entries to the cache and the `value` is `undefined`, no
entry should be added to the `lruHash`

src/ng/cacheFactory.js

@@ -159,13 +159,13 @@ function $CacheFactoryProvider() {
          * @returns {*} the value stored.
          */
         put: function(key, value) {
+          if (isUndefined(value)) return;
           if (capacity < Number.MAX_VALUE) {
             var lruEntry = lruHash[key] || (lruHash[key] = {key: key});
 
             refresh(lruEntry);
           }
 
-          if (isUndefined(value)) return;
           if (!(key in data)) size++;
           data[key] = value;