BUG-2402: add FIXMEs and javadoc

This adds an explanation about the interfaces being used and makes an
explicit warning for users to not use the exposed method.

Change-Id: I07753bea7380f7d92165b8ecb1840ee07d36dc06
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-2402: add FIXMEs and javadoc"