[SPARK-19774] StreamExecution should call stop() on sources when a stream fails

## What changes were proposed in this pull request?

We call stop() on a Structured Streaming Source only when the stream is shutdown when a user calls streamingQuery.stop(). We should actually stop all sources when the stream fails as well, otherwise we may leak resources, e.g. connections to Kafka.

## How was this patch tested?

Unit tests in `StreamingQuerySuite`.

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #17107 from brkyvz/close-source.