Default index status is not overridden on saving

Changing a search index provided in code does not change the entity status flag correctly (should be "Overridden" but remains "Default". This also affects the Features export where you cannot export your modified search index.

Cause of the problem: the __sleep() method does not preserve the entity status, so the index is serialized as incomplete object during form create/submit. Attached patch removes critical entity information from the serialization exceptions.