Test ConcurrentDictionary.Contains(KeyValuePair<TKey, TValue>). Covers #16990.
Changed ConcurrentDictionary.Contains(KeyValuePair<TKey, TValue>) to also compare value. Fixes #16990.
Merge pull request #1069 from esdrubal/bug16990

Changed ConcurrentDictionary.Contains(KeyValuePair) to also compare value. Fixes #16990.