vos: do not mix memory allocation methods

vos: do not mix memory allocation methods

ListVLDB mixed memory allocated with xdr_alloc() and memory
allocated with malloc().  This is not safe to do since it is
possible on some platforms for xdr_alloc() to allocated memory
using a method other than the malloc() linked to the vos
executable.

Instead of stealing the xdr_alloc()'d buffer, allocate a new
buffer and copy the contents.

Change-Id: Icdda3d4d0b7c15464fe7f48123f3e0ebed4c2cc5
Reviewed-on: http://gerrit.openafs.org/3600
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>