aklog: Fix overflows in auth_to_path

In the auth_to_path routine, don't use strcpy and strcat when
working with the fixed length pathtocheck buffer. Instead, use
strlcpy and strlcat to ensure that all string operations fit within
the buffer limits.

Caught by coverity (#985762)

Reviewed-on: http://gerrit.openafs.org/9444
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 788a6b67a088e2565c3b47ecb6e594a7b15f2757)

Change-Id: I9abb8ab33da1d72e42764969e5527d443eea9652
Reviewed-on: http://gerrit.openafs.org/11058
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>