This reverts commit f20868bb.

we support only two I2C slaves thus be consistent here, too.

See merge request !24

usually pointing to proper compilator for respective platform.

coupler1 and coupler2 are subscribed over keep-alive network implementation
over Pub/Sub to coupler3.
Coupler3 is sending heart_beats every 10ms and if not heart_beat is received
by coupler1,2 within 50ms they both go to "safe" mode.

Do not subscribe to Pub/Sub in case we actually do not explicitly have configured so. Printouts for better traceability.