Saving a record immediately after unloading a record with the same id fails

[kaeufl]

Given a record in the store with type 'person' and id 'person-1', the following currently fails with ember data >= 2.13:

store.peekRecord('person', 'person-1').unloadRecord();
store.createRecord('person').save();

If the backend returns a payload that again contains the id 'person-1', the save operation fails with the error:
You cannot update the id index of an InternalModel once set. Attempted to update person-1

We run into this issue in an appplication where we can end up with a record being pushed to the store via a websocket push notification before the HTTP POST request initiated by the save operation has returned. We used to workaround this situation by unloading the record in the adapter's createRecord() hook before returning the payload to the store. This has worked until ember data 2.12. This issue thus currently keeps us from upgrading.

Potentially related issues: #5041, #4972, #5006, #4972

[buschtoens]

Just as #4942 this issue is probably caused by #4821. This PR is has given me hours of headaches. 😢

The hack described in #4972 (comment) works for now.

[stefanpenner]

#5126 is merged, will get a release out soon (aiming for tomorrow)

[dmtask]

@stefanpenner When will the new release be released?