fstrace: Don't read uninitialised data on other platforms either

Commit 908105fe8d51551e45692de4e145022138a0356c fixed an off-by-one
error potentially causing a buffer overread in CheckTypes, but only
in the IRIX/AIX version of the function. Apply the same fix to the
code for the other platforms.

Spotted by Andrew Deason.

Reviewed-on: http://gerrit.openafs.org/11185
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 3ab546395536a3c93613dfd53363d380e2c05081)

Change-Id: Iea700be24803d8156f07d1cf0617ba7aa2aa03d5
Reviewed-on: http://gerrit.openafs.org/11196
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>