libafs: Use vcount, not maxvcount to trim vcaches

libafs: Use vcount, not maxvcount to trim vcaches

Every five minutes we afs_ShakeLooseVCaches to try and return the
number of vcaches in use down to the originally configured -stat level
(when we are using dynamic vcaches). We should calculate how many
vcaches to flush based on the number of currently active vcaches
(afs_vcount), not the peak number (afs_maxvcount). Otherwise, once we
exceed the configured -stat level, we will always keep trying to flush
numerous vcaches, even if we barely have any vcaches in use.

Change-Id: I875fc1d33c817dde2230946b852bb74f8ffd84c2
Reviewed-on: http://gerrit.openafs.org/4584
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>