Don't re-throw exceptions from default FiberManager exception handler
Don't re-throw exceptions from default FiberManager exception handler

Summary: It's very unlikely that caller will handle such exceptions and FiberManager can proceed even if one task failed. DFATAL will ensure we still fail on such exceptions in debug builds.

Reviewed By: yfeldblum

Differential Revision: D3273573

fb-gh-sync-id: 55eba19c16429a3c89a2fdf5363fd4b55b3998a2
fbshipit-source-id: 55eba19c16429a3c89a2fdf5363fd4b55b3998a2

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