nfsd4: use callback security parameters in create_session

We're currently ignoring the callback security parameters specified in
create_session, and just assuming the client wants auth_sys, because
that's all the current linux client happens to care about.  But this
could cause us callbacks to fail to a client that wanted something
different.

For now, all we're doing is no longer ignoring the uid and gid passed in
the auth_sys case.  Further patches will add support for auth_null and
gss (and possibly use more of the auth_sys information; the spec wants
us to use exactly the credential we're passed, though it's hard to
imagine why a client would care).

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index df33e78..bff856c 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -250,6 +250,7 @@
 #define NFSD4_CLIENT_CB_FLAG_MASK	(1 << NFSD4_CLIENT_CB_UPDATE | \
 					 1 << NFSD4_CLIENT_CB_KILL)
 	unsigned long		cl_flags;
+	struct rpc_cred		*cl_cb_cred;
 	struct rpc_clnt		*cl_cb_client;
 	u32			cl_cb_ident;
 #define NFSD4_CB_UP		0