Homestyx hydra

R1:9b21274138cf

Allow `PhabricatorRepositoryCommitHeraldWorker` to continue on certain types of exceptions

Summary: Fixes T6922. We should allow the commit pipeline to continue on certain types of exceptions, including `PhabricatorApplicationTransactionNoEffectException`.

Test Plan:
**Before**
```lang=bash
> ./bin/repository reparse --herald rP2660b944bed4e4dde3e66303656b1d96d8b03e9b
[2015-01-10 09:38:06] EXCEPTION: (PhabricatorApplicationTransactionNoEffectException) Transactions have no effect:
- Edges already exist…
Repository: R1 hydra
Commit Date: Jan 9 2015