t/lib-git-p4: use test_path_is_missing()

Previously, cleanup_git() would use `test_must_fail test -d` to ensure
that the directory is removed. However, test_must_fail should only be
used for git commands. Use test_path_is_missing() instead to check that
the directory has been removed.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-git-p4.sh

@@ -175,7 +175,7 @@ stop_and_cleanup_p4d () {
 
 cleanup_git () {
 	retry_until_success rm -r "$git"
-	test_must_fail test -d "$git" &&
+	test_path_is_missing "$git" &&
 	retry_until_success mkdir "$git"
 }