This is somewhat related to [SPARK-6154](https://issues.apache.org/jira/browse/SPARK-6154), though it only touches Kafka, not the jline dependency for thriftserver.

I tested this locally on 2.11 (./run-tests) and everything looked good (I had to disable mima, because `MimaBuild` harcodes 2.10 for the previous version -- that's another PR).

Author: Iulian Dragos <jaguarul@gmail.com>

Closes #6149 from dragos/issue/spark-2.11-kafka and squashes the following commits:

aa15d99 [Iulian Dragos] Add Kafka modules to the 2.11 build.