NFSv4: Ensure we do not reuse open owner names

The NFSv4 spec is ambiguous about whether or not it is permissible
to reuse open owner names, so play it safe. This patch adds a timestamp
to the state_owner structure, and combines that with the IDA based
uniquifier.
Fixes a regression whereby the Linux server returns NFS4ERR_BAD_SEQID.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4state.c

@@ -393,6 +393,7 @@ nfs4_remove_state_owner_locked(struct nfs4_state_owner *sp)
 static void
 nfs4_init_seqid_counter(struct nfs_seqid_counter *sc)
 {
+	sc->create_time = ktime_get();
 	sc->flags = 0;
 	sc->counter = 0;
 	spin_lock_init(&sc->lock);