nfsd: Fix lease time to 90 seconds

The nfsd default lease time has been changed from 90 seconds to
45 seconds between Linux 4.14 and 4.19 by commit d6ebf5088f09
("nfsd4: return default lease period").

After the upgrade of a nfs server (claptrap) from 4.14 to 4.19, we
saw a failing process ("arplisten") and dmesg logs "NFS:
nfs4_reclaim_open_state: Lock reclaim failed!" on a client (moep,
4.14.87).  The client had the file system mounted with vers=4.0.

Network trace indicated, that the client continued to use the
90 seconds lease period of the previous server incarnation and
sent RENEWs every 60 seconds (2/3 of 90 seconds).  Sometimes the
server answered with NFS4ERR_EXPIRED.

When this happened, the client executed recovery (SETCLIENTID...) but
did non query the server for a new lease_time.  So the problem was
persistent even after the first failure.

As an experiment, I've also restarted a server with the lease time
decrement from 90 to 45 seconds, but the grace period fixed to
90 seconds. Now the client got NFS4ERR_STALE_CLIENTID  but still did
not query the server for a new lease_time and continued to send RENEWs
in 60 second intervals.

Add flags `--lease-time 90 and --grace-time 90` to nsfd to avoid upgrade
complexity. Also change existing option `-N 3` to long form
`--no-nfs-version 3` for readability.

A `systemctl daemon-reload && systemctl restart nfsd` puts the new
value into place as can be verified by `cat /proc/fs/nfsd/nfsv4leasetime`.

misc_systemd_units/nfsd.service

@@ -8,7 +8,7 @@ After=local-fs.target proc-fs-nfsd.mount var-lib-nfs-rpc_pipefs.mount unbound.se
 ExecStartPre=/bin/mkdir -p /var/lib/nfs/v4recovery
 ExecStartPre=/usr/sbin/exportfs -ra
 ExecStart=/usr/sbin/rpc.mountd --foreground --manage-gids
-ExecStartPost=/usr/sbin/rpc.nfsd -N 3 64 ; /usr/sbin/sm-notify
+ExecStartPost=/usr/sbin/rpc.nfsd --lease-time 90 --grace-time 90 --no-nfs-version 3 64 ; /usr/sbin/sm-notify
 ExecReload=/usr/sbin/exportfs -ra
 ExecStopPost=/usr/sbin/rpc.nfsd 0 ; /usr/sbin/exportfs -ua
 Restart=always