watchman: exit 1 if we fail to lock the pid file
watchman: exit 1 if we fail to lock the pid file

Summary: We were returning code 0 which is misleading at best.

Reviewed By: chadaustin

Differential Revision: D22610900

fbshipit-source-id: 9f1bbf175fa96d53f647474dd401e451941d11e1

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