allow for existing local Kafka

[lxghtless]

Feature Request:

Problem:
'Port 9092 is taken by PID:XXXX'

Caused By:
I run the Confluent Platform locally for daily development.

Workaround:
confluent stop or confluent destroy... then make quick-start

Feature Request:
Allow use of an existing local Kafka setup, as this disrupts local development workflows for developers like myself that use Kafka in other projects on a daily basis.

[rabbah]

If there's interest in this, we're happy to accept a PR. The kubernetes and ansible deployment allow for external kafka.