upserver: Don't overflow file and hostname buffers

upserver: Don't overflow file and hostname buffers

If the user specifies a ridiculously long command line, don't
overflow the filename or hostname buffers with what they supply.

Caught by coverity (#985911)

Reviewed-on: http://gerrit.openafs.org/9546
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit d672d5ee78d7673f3c42a7a343989b2bd4dca02b)

Change-Id: Id86f5488bfb3bbf5794af43e9f8fe84a2fe796c3
Reviewed-on: http://gerrit.openafs.org/11064
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>