Ignore return values more harder

Ignore return values more harder

Building on Ubuntu 14.04 with gcc 4.8.2-19ubuntu1, we encounter
fatal warnings about unchecked return values in uss, which is
now always built, as of 00a33b26d74aa067086ddc340efb82184715857f.

Change-Id: I997dcb683e33902c2765121c70bdcf21e9d5e892
Reviewed-on: http://gerrit.openafs.org/11757
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams <3chas3@gmail.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>