Adding failing test for DDC-2230

Proxies that implement the Doctrine\Common\PropertyChangedListener are getting eagerly
initialized because the UnitOfWork injects itself into them after they are created.
The test currently fails for what described above, and also verifies if the UoW
is correctly injected in the proxy during lazy loading.
Applying fix for failing test for DDC-2230
Merge pull request #589 from Ocramius/hotfix/DDC-2230

Hotfix for DDC-2230