Respond to comments from jhutz and Simon

Also add a new error code.

Change-Id: Ibc8300fe13688fd6c51ff0165242695e699af030
Add description for RXGK_BAD_QOP

Change-Id: I8b9f25ea4962841c1a0efecb7847387993bf31e0
Edit

Change-Id: I9f41d14a71abfa68050f777d7f515cde60e17d7f
Roll changelog

Change-Id: Ie5602e02f29bf1026a1fec3de03f4bbdc328852e
Make draft-wilkinson-afs3-rxgk-07

Change-Id: Ia674790c8855a8653fc3333b207ff0f9c493c76d