The minixfs library only ever submits vector elements (and reads) of
the system page size. The test implementation was expecting vector
elements (and reads) of the file system block size. The resulting
mismatch caused I/O to fail in various ways, even though this did not
have an effect on the actual test.
Change-Id: I02f4a3efcd4a32916435d82c7d5798e6b78f0a27