[test] Add hio_seek SEEK_END test

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Check if module was correctly loaded from memory

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Fix module loading from memory

If we're loading a module from memory, don't compute the file md5 digest
because we don't know the file size. Also fix memory pointer update in
hio_read().

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>