[SPARK-2844][SQL] Correctly set JVM HiveContext if it is passed into Python HiveContext constructor

https://issues.apache.org/jira/browse/SPARK-2844

Author: Ahir Reddy <ahirreddy@gmail.com>

Closes #1768 from ahirreddy/python-hive-context-fix and squashes the following commits:

7972d3b [Ahir Reddy] Correctly set JVM HiveContext if it is passed into Python HiveContext constructor