OAK-1726 - Improve support for local caching in DataStoreBlobStore

Pass the right instance for config setting

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1587806 13f79535-47bb-0310-9956-ffa450edef68
OAK-1726 - Improve support for local caching in DataStoreBlobStore

Update docs

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1587807 13f79535-47bb-0310-9956-ffa450edef68