[BUGFIX] New test and possible fix for issue #7265 (self-referent rel)

[davelindquist-egistix]

This addresses issue #7265 (Self-Referent Relationship in Save Response Blows Up Save).

It includes a new test that replicates the problem - saving a record, and having the 'backend' return a relationship that is self-referent, thus blowing up Ember Data when it checks to see if the just-saved id has already been used. (Said id was added to the store as part of the relationships-handling.)

It also includes a patch to record-data.ts that solves the problem in the test, and does not cause any other tests to fail. HOWEVER, it does this by simply re-ordering the handling of relationships and the 'set the record id' call - I don't know if there is a reason that they were done in the opposite order originally, and thus don't know for certain if this will break something else. (I'm hoping the tests would have shown that, but perhaps wiser eyes can take a look to make certain.)

Thanks!

[davelindquist-egistix]

Hmm, it appears that Travis runs additional tests beyond what happens with the tests locally, and these have failed. I will close this PR, and resubmit one with only the test in it.

[runspired]

Did you ever resubmit? The fix here is simple enough I'd be ok with it since it slightly improves the situation (most of the time this sort of case doesn't have such an easy way to address it in the internals). I'd be happy to look at whatever failed and see if this could work.

[runspired]

Confirmed this test passes against master so closing, but I like the ordering change and test since they make more sense anyway so am porting these to a new PR.