(#2685) - shows conflicts when there are none

@daleharvey Correct me if I'm wrong, but shouldn't the `_conflicts` array be empty in these cases? For the remote db it's returning `['1-cf398aa8cceefcf9b8484d02bdaee3fe']` and for the local one, `['2-cf398aa8cceefcf9b8484d02bdaee3fe']`. Very bizarre.
This used to have an `if (src.type() === 'http')` around it, so we only used this optimization for http adapters. But now that `allDocs` is fixed in all three adapters, we can use this optimization everywhere.