watchman: remove use of json_unpack from clock command
watchman: remove use of json_unpack from clock command

Summary: as above

Reviewed By: chadaustin

Differential Revision: D17779609

fbshipit-source-id: 53383b8aabf649600ecc851aed4940703f906209

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