Failing tests
Helper for LRU LinkedHashMap
Maintain cache as desired.
Use CacheMap for other derived LinkedHashMap
Rename new class for clarity
Another test that goes through full stack
merge nathanlws: Fix TreeService Exchange caching

Merge pull request #1079 from nathanlws/sql-layer/fix-tree-service-exchange-caching
https://github.com/FoundationDB/sql-layer/pull/1079