test: compare raw output, not mangle tabs and spaces

test: compare raw output, not mangle tabs and spaces

Before comparing with the expect file, we used to call function
"make_user_friendly_and_stable_output" to filter out trailing spaces in
output.  Ævar recommends using pattern "s/Z$//" to prepare expect file,
and then compare it with raw output.

Since we have fixed the issue of occasionally missing the clear-to-eol
suffix when displaying sideband #2 messages, it is safe and stable to
test against raw output.

Suggested-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>