Operate in --kvstore mode

[squaremo]

If the driver is used with dockers connected to a shared database (currently, this is determined with a --kvstore flag to docker (and the driver being marked as Global(?)), all plugin processes will see each create and delete call.

• In the case of CreateEndpoint, nodes other than the one that received the command get a populated interfaces list.
• In the case of CreateNetwork, there is nothing to distinguish the calls.
• Join and Leave requests only happen on the node where the command happened
• DeleteEndpoint is called identically on all nodes
• DeleteNetwork is called identically on all nodes

If our operations are either local or idempotent, all we need (ha!) is that everything is propagated in the correct order. That means:

• endpoint creation can be ignored if the interfaces already exist;
• endpoint deletion can just release the IP (if it's a local one? if it fails on other hosts that's fine)
• network creation has to be a "first one wins, others get the information" operation
• network deletion has to be "first one succeeds, everyone else succeeds or fails trivially" operation

[bboreham]

Docker moved on from this design so closing as obsolete.