rxgen: Silence some uninitialised variable warnings

Change-Id: Ida939533afbbf2afb81cce44ea6693d33c172062
Reviewed-on: http://gerrit.openafs.org/9157
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>