staging: lustre: info leak in lnet_ping()

On 64 bit systems there is a 4 byte hole after the last member of the
struct.  We should clear it to avoid disclosing stack information.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>