s4: torture: Tweak the compound padding streamfile test to send 3 reads instead of...

s4: torture: Tweak the compound padding streamfile test to send 3 reads instead of 2, and check the middle read padding.

The protocol allows the last read in a related compound to be split
off and possibly go async (and smbd soon will do this). If the
last read is split off, then the padding is different. By sending
3 reads and checking the padding on the 2nd read, we cope with
the smbd change and are still correctly checking the padding
on a compound related read.

Do this for the stream filename compound padding test.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>