Add exclude-dir to check_is_private_key_nor_password_is_not_logged script

Because as can be observed there:
https://gitlab.syncad.com/hive/clive/-/jobs/1260490#L88

test-tools seems to log all envrionment variables which also include
CI_COMMIT_MESSAGE during CI and when e.g "password" text is used in
the commit name, there will be a false positive.