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.
I wasn't sure if that would mean the supervisor would try to restart it causing a loop causing the vm to shut down. Would it?