Adding content with local=true causes allocation imbalances

[hsanjuan]

When adding with local=true, we ensure that the local peer is among the dag-service destinations which become the pin allocations. That ensures that the peer on which the content is added will become one of the pinners. This is done here by replacing the last allocation with the local peer ID.

But this is actually very naïve and breaks the balanced allocations setup as we have no idea what peer we are replacing. We can end up with pins allocated multiple times to the same region for this reason.

Editing the allocations for the pin should not happen here. Destinations should be correctly set from the moment things are allocated. The local peer should just be a priority peer when local=true is set. This is related to #1764 as well, as that should be fixed in advanced.