[Streaming][Kinesis][SPARK-20168] Could I get some reviews of the patch that resolves kinesis timestamp resume

[Yash Sharma]

Hi Team,
Could I get some review at the patch here. Would love to hear suggestions
here on the patch. I had to reopen SPARK-20168 because of this bug.

https://github.com/apache/spark/pull/21541
https://issues.apache.org/jira/browse/SPARK-20168

Cheers,
Yash