Revert "nfsd4: return default lease period"

Revert "nfsd4: return default lease period"

This reverts commit e333f32796ef1b5864e8a8e391dd133cd01f05ec.

I forgot that the kernel's default lease period should never be
decreased!

After a kernel upgrade, the kernel has no way of knowing on its own what
the previous lease time was.  Unless userspace tells it otherwise, it
will assume the previous lease period was the same.

So if we decrease this value in a kernel upgrade, we end up enforcing a
grace period that's too short, and clients will fail to reclaim state in
time.  Symptoms may include EIO and log messages like "NFS:
nfs4_reclaim_open_state: Lock reclaim failed!"

There was no real justification for the lease period decrease anyway.

Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Fixes: e333f32796ef "nfsd4: return default lease period"
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>