DAFS: Raise LogLevel for per-chain vol stats

DAFS: Raise LogLevel for per-chain vol stats

Only report detailed per-chain volume statistics on shutdown/SIGXCPU
if LogLevel is 125 (or 25 for smaller per-chain stats). If a
fileserver is configured with a large -vhashsize, printing out stats
for each chain can take awhile and use up a nontrivial amount of disk
space for logging, so only print out these stats if we're asked for
them.

Change-Id: Iceb38e29ab40958e05f3cf146687f679bd0f061c
Reviewed-on: http://gerrit.openafs.org/2759
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>