The previous commit set status.displayCommentPrefix file-wide in
t7060-wtstatus.sh, t7508-status.sh and t/t7512-status-help.sh to make the
patch small. However, now that status.displayCommentPrefix is not the
default, it is better to disable it in tests so that the most common
situation is also the most tested.

While we're there, move the "cat > expect << EOF" blocks inside the
tests.
Signed-off-by: NMatthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>