cut unnecessary use of folly::try_and_catch
cut unnecessary use of folly::try_and_catch

Summary: Prefer just to use the usual C++ `try` and `catch` unless the use-case requires the additional functionality of `folly::try_and_catch`.

Reviewed By: edenzik

Differential Revision: D26877191

fbshipit-source-id: c86a2160b4c577b515b89f25dece3f724784f993

facebook/mcrouter,facebook/mcrouter,facebook/mcrouter,facebook/mcrouter