nfs4: server should warn if '/var/nfs/v4_state' doesn't exist
/var/nfs/v4_state and /var/nfs/v4_oldstate are used to keep nfs4-client states.
nfs4-client states are used during reclamation period (when server rebooted or restarted).
If v4_state or v4_oldstate directories don't exist, server can't load previously saved client's states
and clients get NFS4ERR_NOGRACE error during reclamation.
Adding warning will help to diagnose this situation.