turn off strict symlink check in OpenFileHandleOptions.openDir().
turn off strict symlink check in OpenFileHandleOptions.openDir().

Summary:
Use OpenFileHandleOptions.strictOpenDir() to enable the strict symlink
rules explicitly.

Before this change, `watchman::openFileHandle()` always enforces strict
symlink rules because `strictNameChecks` is true even in
`OpenFileHandleOptions.openDir()`.
Closes https://github.com/facebook/watchman/pull/478

Differential Revision: D5180611

Pulled By: wez

fbshipit-source-id: b04c8e12328325dffe2752414f4795d56aebd851

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