libadmin: Don't free garbage

Make sure that we initialise the nbulkentries structure to 0 before
we start work, so that if the failure handler is called, it doesn't
try to free garbage.

Caught by coverity (#985980)

Reviewed-on: http://gerrit.openafs.org/9317
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit bf78bf2c115659b78c34d3bc9d1934bcff21c8cc)

Change-Id: I24536b0bec47f381eee7cfcbe1feb89c373cca0f
Reviewed-on: http://gerrit.openafs.org/11030
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>