afs: fs getcacheparms miscounts zero-length dcaches

afs: fs getcacheparms miscounts zero-length dcaches

When fs getcacheparms is issued with the -excessive option, it
tabulates all in-memory dcaches ("DCentries") by size.

dcaches with validPos == 0 were being tabulated in the 4k-16k bucket.

Fix the first comparison in the 'sieve' so these dcaches will be counted
in the correct 0-4k bucket instead.

Introduced by commit 176c2fddb95ced6c13e04e7492fc09b5551f273c

Reviewed-on: https://gerrit.openafs.org/12346
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit c966c0b8414ef0a041b1a8d5261c9eccd4d39d99)

Change-Id: I53a20644f549550cef85f0cc6f3551ed5dbe1e23
Reviewed-on: https://gerrit.openafs.org/12604
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>