nfsd4: hash closed stateid's like any other

Look up closed stateid's in the stateid hash like any other stateid
rather than searching the close lru.

This is simpler, and fixes a bug: currently we handle only the case of a
close that is the last close for a given stateowner, but not the case of
a close for a stateowner that still has active opens on other files.
Thus in a case like:

	open(owner, file1)
	open(owner, file2)
	close(owner, file2)
	close(owner, file2)

the final close won't be recognized as a retransmission.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
index d6aec4f..da68bf6 100644
--- a/fs/nfsd/state.h
+++ b/fs/nfsd/state.h
@@ -76,7 +76,9 @@
 #define NFS4_OPEN_STID 1
 #define NFS4_LOCK_STID 2
 #define NFS4_DELEG_STID 4
-	char sc_type;
+/* For an open stateid kept around *only* to process close replays: */
+#define NFS4_CLOSED_STID 8
+	unsigned char sc_type;
 	struct list_head sc_hash;
 	stateid_t sc_stateid;
 };