kernel32/tests: use ret in load_blackbox()

[Dmitry Timoshkov]

Austin English <austinenglish at gmail.com> wrote:

>      ret=ReadFile(hFile, blackbox, size, &read, NULL);
> +    ok(ret, "ReadFile failed: %08x\n", GetLastError());

Printing last error without prior setting it to 0xdeadfeef won't really
help. Also errors returned by GetLastError() are defined in decimal in
winerror.h.

-- 
Dmitry.