Wrong test value for default timeout in OTLP Exporter Mixin

[ocelotl]

          Either I don't understand the change or there is a new bug here. How can it be correct to change `start_time` and `now` from seconds to nanoseconds without changing the `30 / 1000`?

Secondly, does anyone understand what this assert is supposed to do? I understand it somehow like: "Ensure that the shutdown took at least 30 seconds.". If this is the case, shouldn't it be 30 * 1000 then originally and now `30 * 1e9?

Originally posted by @LarsMichelsen in #4014 (comment)