reflow1.17.0

Highlights from this release:

• digests of resolved filesets of exec dependencies are now shown in log output
• minor fixes to taskdb setup
• replace execlog/syslog with a single run log
• improvements to reflow ec2instances tool, including an option to show spot placement scores by AZ
• expedite spot request failure upon low capacity
• upgraded aws-sdk-go to v1.42.0
• other minor changes related to AWS region configuration