Possible Race Conditions

[ppashakhanloo]

I believe I have found some concurrency bugs that seem contrary to the fact that LruCacheNet is supposed to be a thread-safe library. Here are the bugs:

The following functions cannot be safely called from two concurrent threads since LruCacheNet.CacheEnumerator does not seem to be thread-safe:

1. Racing on LruCacheNet.CacheEnumerator.current:
   1.1. LruCacheNet.CacheEnumerator.MoveNext()
   1.2. LruCacheNet.CacheEnumerator.Reset()
   1.3. LruCacheNet.CacheEnumerator.Dispose()

2. Racing on LruCacheNet.CacheEnumerator.cache:
   2.1. LruCacheNet.CacheEnumerator.Dispose()

3. Racing on LruCacheNet.CacheEnumerator.head:
   3.1. LruCacheNet.CacheEnumerator.Dispose()
   3.2. LruCacheNet.CacheEnumerator.MoveNext()