NFS: Never use user credentials for lease renewal

Never try to use a non-UID 0 user credential for lease management,
as that credential can change out from under us.  The server will
block NFSv4 lease recovery with NFS4ERR_CLID_INUSE.

Since the mechanism to acquire a credential for lease management
is now the same for all minor versions, replace the minor version-
specific callout with a single function.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index 36e21cb..202e363 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -441,7 +441,7 @@
 	struct rpc_xprt *xprt;
 	struct rpc_cred *cred;
 
-	cred = nfs4_get_exchange_id_cred(session->clp);
+	cred = nfs4_get_clid_cred(session->clp);
 	nfs4_proc_destroy_session(session, cred);
 	if (cred)
 		put_rpccred(cred);