Issue:
We put response headers into the AdditionalData property bag since we don't have a response envelope. This introduces issues when the objects returned in a response are updated, and the sent as the contents for a request. The response headers in the AdditionalData property are serialized and cause an error at the service. While customers shouldn't do this and should use a patch object, we expect this scenario and so we should proactively remove (or not serialize) the response headers from AdditionalData so they aren't sent over the wire.

This was added with:
#260

Why this is an issue:
#270