NFSv4.1: Clear the old state by our client id before establishing a new lease

If the call to exchange-id returns with the EXCHGID4_FLAG_CONFIRMED_R flag
set, then that means our lease was established by a previous mount instance.
Ensure that we detect this situation, and that we clear the state held by
that mount.

Reported-by: Jorge Mora <Jorge.Mora@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4session.h

@@ -70,6 +70,7 @@ struct nfs4_session {
 
 enum nfs4_session_state {
 	NFS4_SESSION_INITING,
+	NFS4_SESSION_ESTABLISHED,
 };
 
 extern int nfs4_setup_slot_table(struct nfs4_slot_table *tbl,