rails/rails — pull request #14326 by arthurnn (2014-03-08 17:55:08+00:00)
Title: Make sure we clean preview_interceptors

backport https://github.com/rails/rails/pull/14318 to 4-1 .

I am 95% that this fixed the mailer issue on travis.

travis is now failing randomly for another reason:
```
1) Error:
MemCacheStoreTest#test_deserializes_unloaded_class:
ArgumentError: key cannot be blank
```

So we should backport this to 4-1-stable. cc @pixeltrix