The info should be updated when the registration has changed. In order
to prevent a stale instance info, the sba client includes a "startup"
timestamp in the metadata as default. So when the instance is restarted
the registration changes and the info is updated, even when the instance
isn't considered as down in between.

To prevent this when using a discovery client you need to add a value
to the metadata which changes with every restart.
(e.g. `random=${random.value}`)

fixes #556