fortify batch information and sha1 requests
fortify batch information and sha1 requests

Summary:
Use range-based for loops in the Eden watcher, and fortify some of
them against Eden returning bogus results for batch information and
SHA-1 lookups.

Reviewed By: wez

Differential Revision: D8956921

fbshipit-source-id: 3c58a4538b9adc84d6f37b390539acbcb7317a92

wez/watchman,nodakai/watchman,nodakai/watchman,facebook/watchman,wez/watchman,nodakai/watchman,wez/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,wez/watchman,wez/watchman,nodakai/watchman,wez/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,wez/watchman,wez/watchman,facebook/watchman,wez/watchman,facebook/watchman