Add HasStorage.getAIS().
merge MMcM: Add HasStorage.getAIS().

Merge pull request #1078 from MMcM/sql-layer/has-storage-has-ais
https://github.com/FoundationDB/sql-layer/pull/1078
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
New HasStorage method