[SPARK-22908][SS] Roll forward continuous processing Kafka support with fix to
continuous Kafka data reader
## What changes were proposed in this pull request?
The Kafka reader is now interruptible and can close itself.
## How was this patch tested?
I locally ran one of the ContinuousKafkaSourc
[SPARK-22908][SS] Roll forward continuous processing Kafka support with fix to
continuous Kafka data reader
## What changes were proposed in this pull request?
The Kafka reader is now interruptible and can close itself.
## How was this patch tested?
I locally ran one of the ContinuousKafkaSourc