[security-services] Wrong top-level status codes listed in sec 3.4.3.1

[Scott Cantor <cantor.2@osu.edu>]

Sorry for not catching this sooner...

The change in terminology to Requester/Responder instead of
Sender/Receiver didn't get made in the listing of the top level codes,
unfortunately. Reference to the correct value is made in at least one
other place in the text, mainly because I supplied that change as well.

This is fairly significant, moreso than perhaps it appears, because of
the other change that removed the enumeration from the schema so as not
to set the namespace prefix used in stone. From an interop standpoint,
people have to know what to switch on because the schema won't kick out
a bad one.

FWIW, I switched to the Req/Res names in my implementation, but then I
knew about the change apart from reading the released spec.

-- Scott