Description:

Probably worth making a quick note of this restriction

Engineering Ticket Description:

We currently allow renameCollection from the "local" database to a replicated database. This doesn't make a lot of sense; the local collections may be different on each replica, so doing so will result in an inconsistent set.

We also allow renameCollection from a replicated DB to an unreplicated one; this usually works but will cause problems if the local collection exists and dropExisting isn't specified.