Rework distributed control bootstrap mechanism

[plorenz]

Raft cluster bootstrap is too easy to get wrong. Change it so that bootstrap happens when the edge is initialized. This will happen when one of the following happens:

1. ziti agent controller init.. is called
2. The cluster is auto-initialized using a configured database

We should also add a cluster UUID which gets passed around when joining members.
Nodes can only join under the following conditions:

1. They have the same cluster id
2. One has a cluster id and the other doesn't
3. Neither has a cluster id set yet