autoDeserialize tests returning null for collections should be positive tests

[sfackler]

What happened?

In the client autoDeserialize tests, there are negative tests for all of the collection-returning endpoints (e.g. receiveListBearerTokenAliasExample) of null. I think the idea is that it's there to test that clients reject a 200 response with a body of null, but the verification server actually sends a 204, which is a valid response according to the spec: https://github.com/palantir/conjure/blob/master/docs/spec/wire.md#31-status-codes

Note that the response for test 2 of receiveListBearerTokenAliasExample (the null test) returns 204 in packet 247.

What did you want to happen?

These should either be moved to positive tests, or the verification server should return a 200.