tests/03r5assemV1: reduce sync speed further.

tests/03r5assemV1: reduce sync speed further.

This test is quite sensitive to resync speed - if the resync happens
to quickly it fails because it sees aan optimal array when it expects
a degraded array.
1000 is often slow enough but now always, so slow it down even more.
This requires reducing speed_limit_min also as kernel ignores 'max'
when speed is below 'min'.

Reported-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>