fstrace: Remove redundant variable assignment

Don't reset the value of 'code' when nothing else references it.

Caught by clang-analyzer

Change-Id: Ifd361ed6eb8c6b8740466f6c1a337669160874f4
Reviewed-on: http://gerrit.openafs.org/9191
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>