Unix CM: Remove unused security class initialisation

Caught by clang-analyzer

Change-Id: Iab28a305ae377cabc455132fde3b90146921100b
Reviewed-on: http://gerrit.openafs.org/9152
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>