order byte of the two byte transfer length field or not.
Since the maximum size of a std vpd page takes 260 bytes to transfer
and some targets send this much, testing and comparing the returned buffer
between allocation length == 255 and == 256 doesnt work.
Instead change test to verify that allocation length 511 and 512 returns the same amount and content of data.
This test then still allows finding targets that only look at the low order byte
(which is 0xff for 511 but is 0 for 512)
