test-lib: fix GIT_EXIT_OK logic errors, use BAIL_OUT

test-lib: fix GIT_EXIT_OK logic errors, use BAIL_OUT

Change various "exit 1" checks that happened after our "die" handler
had been set up to use BAIL_OUT instead. See 234383cd401 (test-lib.sh:
use "Bail out!" syntax on bad SANITIZE=leak use, 2021-10-14) for the
benefits of the BAIL_OUT function.

The previous use of "error" here was not a logic error, but the "exit"
without "GIT_EXIT_OK" would emit the "FATAL: Unexpected exit with code
$code" message on top of the error we wanted to emit.

Since we'd also like to stop "prove" in its tracks here, the right
thing to do is to emit a "Bail out!" message.

Let's also move the "GIT_EXIT_OK=t" assignments to just above the
"exit [01]" in "test_done". It's not OK if we exit in
e.g. finalize_test_output.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>