aklog: those pesky assignments in conditionals

This one should actually be an assignment, and the compiler warning
for having two sets of parentheses is helpful.

Found by clang on FreeBSD 10.0.

Change-Id: Ic906cbdc50a20bcd0b91555581b60c518da2bc81
Reviewed-on: http://gerrit.openafs.org/10823
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Perry Ruiter <pruiter@sinenomine.net>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: D Brashear <shadow@your-file-system.com>