NFS: Don't accept more reads/writes if the open context recovery failed

If the state recovery failed, we want to ensure that the application
doesn't try to use the same file descriptor for more reads or writes.

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

include/linux/nfs_fs.h

@@ -77,6 +77,7 @@ struct nfs_open_context {
 	unsigned long flags;
 #define NFS_CONTEXT_ERROR_WRITE		(0)
 #define NFS_CONTEXT_RESEND_WRITES	(1)
+#define NFS_CONTEXT_BAD			(2)
 	int error;
 
 	struct list_head list;