nfsd4: use auth_unix unconditionally on backchannel

This isn't actually correct, but it works with the Linux client, and
agrees with the behavior we used to have before commit 80fc015bdfe.

Later patches will implement the spec-mandated behavior (which is to use
the security parameters explicitly given by the client in create_session
or backchannel_ctl).

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 0840fc4..c8e9f63 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -645,7 +645,6 @@
 		.timeout	= &timeparms,
 		.program	= &cb_program,
 		.version	= 0,
-		.authflavor	= clp->cl_flavor,
 		.flags		= (RPC_CLNT_CREATE_NOPING | RPC_CLNT_CREATE_QUIET),
 	};
 	struct rpc_clnt *client;
@@ -656,6 +655,7 @@
 		args.client_name = clp->cl_principal;
 		args.prognumber	= conn->cb_prog,
 		args.protocol = XPRT_TRANSPORT_TCP;
+		args.authflavor = clp->cl_flavor;
 		clp->cl_cb_ident = conn->cb_ident;
 	} else {
 		if (!conn->cb_xprt)
@@ -665,6 +665,7 @@
 		args.bc_xprt = conn->cb_xprt;
 		args.prognumber = clp->cl_cb_session->se_cb_prog;
 		args.protocol = XPRT_TRANSPORT_BC_TCP;
+		args.authflavor = RPC_AUTH_UNIX;
 	}
 	/* Create RPC client */
 	client = rpc_create(&args);