Removes threading from common_consumer

It appears KafkaConsumer is not threadsafe, and it was generating
issues regarding the sending of heartbeats, causing kafka to kill
connections and causing coordinator dead errors.
Also removes heartbeat and session timeouts from consumer config.
They were generating conflicts with different default request
timeouts, and were in place to leverage issues regarding what is
mentioned above.

Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>