Model#_findFetchMany doesn't find sideloadedData

[forumm]

After side loading data into a model, find yields inconsistent results when called with single id vs. array of ids.
_findFetchMany calls into the adapter to fetch the records again.
where as _findFetchById returns the record from the cache.

[ebryn]

Can we get a failing test?

[ebryn]

Closing in favor of #315