Log an error, instead of crashing, when Sputnik API is missing

Esputnik has to be started temporarily today as it crashes when the config is missing. This commit changes that behaviour, and  instead of crashing it will log an error for every message it cannot send.

These commits also add a test for this behaviour.
Why not stop here instead of having the server start. Is the idea that we want to be able to set the URL later possibly?