[DataStore] Unauthorized errors should be ignored in SyncProcessor

[richardmcclellan]

Currently, when a sync request returns an Unauthorized error for one of the models, the sync engine is stopped. This is not ideal, because if an Unauthorized error occurs with just a subset of types, we shouldn't prevent customers from making being able to sync and query for the other types. Instead, we should catch the errors and move on to sync the next model.

The JS library already behaves this way (see this code reference)