Cosmetic change.

Pick up cosmetic changes from https://review.openstack.org/#/c/80127/10
* rename exec_flow_context to task_runtime_context.
* Fix comments to start with cap letter and end with a period.

Change-Id: Ic74f045f8d401053a983b1f6356a8d3562b23f2e
Merge "Cosmetic change."