Associations loaded in 'loadClassMetadata' event are not well initialized inside ClassMetadata

Reproduce
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• I have an entity
• I'm loading an association (named 'myfield') inside a `LoadClassMetadata` event.

Error
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Then i get this error : Notice: Undefined index: myfield in /vendor/doctrine/lib/Doctrine/ORM/UnitOfWork.php line 2473

Problem
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It seems that here https://github.com/doctrine/doctrine2/blob/master/lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php#L294 we call the method 'wakeupReflection' before the loadClassMetadata event is dispatched.

A solution
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I've created a patch (all tests pass) here https://github.com/gordonslondon/doctrine2/commit/0823cd54d0b2720f5e72aa9a29d16271904d99f0 that fixed the issue. Do you want a PR ?

Here's the PR : https://github.com/doctrine/doctrine2/pull/264