t9903: fix broken && chain

We might wonder why our && chain check does not catch this case:
The && chain check uses a strange exit code with the expectation that
the second or later part of a broken && chain would not exit with this
particular code.

This expectation does not work in this case because __git_ps1, being
the first command in the second part of the broken && chain, records
the current exit code, does its work, and finally returns to the caller
with the recorded exit code. This fools our && chain check.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9903-bash-prompt.sh

@@ -177,7 +177,7 @@ test_expect_success 'prompt - interactive rebase' '
 	git checkout b1 &&
 	test_when_finished "git checkout master" &&
 	git rebase -i HEAD^ &&
-	test_when_finished "git rebase --abort"
+	test_when_finished "git rebase --abort" &&
 	__git_ps1 >"$actual" &&
 	test_cmp expected "$actual"
 '