initial ip address space allocation is highly sub-optimal when using subnets

[bboreham]

Currently, if 4 peers form a consensus at start-up then each one gets 1/4 of the whole space, in one big piece. If a peer goes down, having such a large contiguous chunk of space inaccessible may be painful, especially with multi-subnet ipam.

If we inserted more tokens into the initial ring, such that each peer still has 1/4 of the space but it is less likely to cover any particular range, this might be easier to live with. Though weave status will get much more verbose.