Add support for modern `requests` versions

Signed-off-by: Tomas Sedovic <tomas@sedovic.cz>
Python client: fix the instance key colection

The recent JSON API fixes changed the format of the key-related response
bodies, breaking the client.

Signed-off-by: Tomas Sedovic <tomas@sedovic.cz>
Python client: update the ip addresses format

Signed-off-by: Tomas Sedovic <tomas@sedovic.cz>