Proper Session Test

Maybe to close but especially to show a non-working example without `self::start()` in `CakeSession::delete()`. If you remove `self::start()` you will see an error occurres.

Refs: https://github.com/cakephp/cakephp/pull/4405
Keeping the `self::start()` you added in `delete()` and using this patch, running `cake test core Model/Datasource/CakeSession --stderr --filter testDeleteCli` the first assert fails as expected. But `cake test core Model/Datasource/CakeSession --stderr` doesn't fail.

After removing the start() from delete(), this assert fails for both  `cake test core Model/Datasource/CakeSession --stderr`  and  `cake test core Model/Datasource/CakeSession --stderr --filter testDeleteCli` as expected :)

So like I said testing this in CLI is difficult due to lack of cookie. Unless you can provide some e.g. controller code to reproduce the problem I am inclined to revert your original patch.