Record backoff duration in status dynamic
Record backoff duration in status dynamic

Summary: So it shows up in task logs.

Reviewed By: agoder

Differential Revision: D2594088

fbshipit-source-id: ce6974c6d3960cbf7a10c41eb77eb6c37e077633

facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro,facebook/bistro