afs: silence bogus warning about dcListCount uninitialized

afs: silence bogus warning about dcListCount uninitialized

Commit 3be5880d1d2a0aef6600047ed43d602949cd5f4d 'afs: Avoid panics in
afs_InvalidateAllSegments' is correct, but at least one compiler (gcc
4.3.4 on SLES 11.3) is fooled into issuing a warning:

    [...]/afs_segments.c: In function 'afs_InvalidateAllSegments_once':
    [...]/afs_segments.c:506: error: 'dcListCount' may be used uninitialized in this function

To silence the bogus warning, initialize dcListCount when defined.

Change-Id: I5938c85c71d08ed61ec1f69a50afb19c9b31fa82
Reviewed-on: https://gerrit.openafs.org/14048
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>