miscellaneous server patches

[J. Bruce Fields]

None of this is urgent.  The first three are just random bits I've had
sitting in my tree, and that you already have in at least one case.

The fourth shares the grace period calculation between lockd and nfsd4,
closing the obvious race that could occur when they end their grace
periods at different times.  I've been holding off just because the
nfsv4 server reboot recovery code is in some sort of limbo--we've been
meaning to replace it, but the replacement isn't ready yet.

But any replacement is going to do something very similar, and I think
it'd be useful to have this dealt with when we deal with the HA failover
stuff.

This actually still leaves open a small window where a lockd client
could get a lock before the nfsv4 grace period is completely finished;
fixing that:

	http://linux-nfs.org/cgi-bin/gitweb.cgi?p=bfields-2.6.git;a=commit;h=cf8c96007eb55851fbbaf53cdacab63d626b7c0a

requires some more locking, and seems like overkill for now.

--b.