[SPARK-3615][Streaming]Fix Kafka unit test hard coded Zookeeper port issue

Details can be seen in [SPARK-3615](https://issues.apache.org/jira/browse/SPARK-3615).

Author: jerryshao <saisai.shao@intel.com>

Closes #2483 from jerryshao/SPARK_3615 and squashes the following commits:

8555563 [jerryshao] Fix Kafka unit test hard coded Zookeeper port issue
[SPARK-546] Add full outer join to RDD and DStream.

leftOuterJoin and rightOuterJoin are already implemented.  This patch adds fullOuterJoin.

Author: Aaron Staple <aaron.staple@gmail.com>

Closes #1395 from staple/SPARK-546 and squashes the following commits:

1f5595c [Aaron Staple] Fix python style
7ac0aa9 [Aaron Staple] [SPARK-546] Add full outer join to RDD and DStream.
3b5d137 [Aaron Staple] In JavaPairDStream, make class tag specification in rightOuterJoin consistent with other functions.
31f2956 [Aaron Staple] Fix left outer join documentation comments.