OPENDJ-1585 CR-5017 Optimize/Fix CompactDn class

- Remove unecessary ByteString wrapping 
- Remove eager version of CompactDn
- Store reference to schema in both DN and CompactDn classes 

git-svn-id: https://svn.forgerock.org/opendj/trunk/opendj@11249 41b1ffd8-f28e-4786-ab96-9950f0a78031