Add MaintainedNodeValue to FakeStoreAdapter

Signed-off-by: John Tuley <jtuley@pivotallabs.com>
Make FakeStoreAdapter more threadsafe

Signed-off-by: Johannes Petzold <jpetzold@pivotallabs.com>
Merge pull request #2 from cloudfoundry/betterFake

Add MaintainedNodeValue to FakeStoreAdapter