Bootstrap Endpoint Address

After Bootstrap returns successfully, get the bootstrap instance and
write its addresses to jenv/environ info/connection info (choose
your name).
Why not just use
  apiInfo, err := environs.APIInfo(environ) ?

If that is dead due to the StateServerInstances call, instead use the useful bits:

```go
	apiPort := config.APIPort()
	apiAddrs := make([]string, len(addrs))
	for i, hp := range network.AddressesWithPort(addrs, apiPort) {
		apiAddrs[i] = hp.NetAddr()
	}
```
Having made sure that the addresses that you have are all public addresses.