comerr: avoid comma operator

Avoid unnecessary use of the comma operator in compile_et's
command-line argument processing.

Reviewed-on: http://gerrit.openafs.org/10491
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Marc Dionne <marc.c.dionne@gmail.com>
Tested-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 15c80b1a92516a41d4aed8403db1485e97a7eff6)

Change-Id: I28f7503877d670406c973520a33924480bb96ad9
Reviewed-on: http://gerrit.openafs.org/11224
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Tested-by: Stephan Wiesand <stephan.wiesand@desy.de>