aklog: Correct size used for strlcpy()

aklog: Correct size used for strlcpy()

When copying into the 'cell' array, use the size of cell, not
the size of some other array that is copied into a few lines previously.

(cherry picked from commit 777870da86e9ed66756e01e858a54e959959482d)

Change-Id: Ib8b523901dd8008038c5a95a7c315b899cff8cee
Reviewed-on: http://gerrit.openafs.org/11807
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-on: http://gerrit.openafs.org/11808
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>