Allow update mode for streaming queries with join

In issue SPARK-19140 we supported update output mode for non-aggregation streaming queries. This should also be applied to streaming join to keep semantic consistent.

PS. Streaming join feature is added after SPARK-19140.

When using update output mode the join will works exactly as append mode. However, for example, this will allow user to run an aggregation-after-join query in update mode in order to get a more real-time result output.