NFSv4.1: don't do two EXCHANGE_IDs on mount

Since the addition of NFSv4 server trunking detection the mount context
calls nfs4_proc_exchange_id then schedules the state manager, which also
calls nfs4_proc_exchange_id. Setting the NFS4CLNT_LEASE_CONFIRM bit
makes the state manager skip the unneeded EXCHANGE_ID and continue on
with session creation.
Reported-by: Jorge Mora <mora@netapp.com>
Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4state.c

@@ -351,6 +351,7 @@ int nfs41_discover_server_trunking(struct nfs_client *clp,
 	status = nfs4_proc_exchange_id(clp, cred);
 	if (status != NFS4_OK)
 		return status;
+	set_bit(NFS4CLNT_LEASE_CONFIRM, &clp->cl_state);
 
 	return nfs41_walk_client_list(clp, result, cred);
 }