more RAII-ish initialization of config_file
more RAII-ish initialization of config_file

Summary: Tidies up loading the `.watchmanconfig` file

Reviewed By: farnz

Differential Revision: D4045280

fbshipit-source-id: d063e0ff5d9492ec1eb89a8a6d8eb4bc59d0ed6e

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