Use server dict instead of IP for load balancer operations in otter.worker.launch_server_v1

This enables us to use node ids as well as IPs, which is necessary for RCv3.
Oops, you beat me to commenting.  I don't remember seeing one in JIRA anywhere - there is a ticket about validating that the user has ServiceNet in their server args if they want a load balancer too.  Because if the user specifies only public net, or only some other network, then we can't add to the load balancer and we get KeyErrors.

There was a previous (done) ticket to not try to extract the private address if we did not need to add to the load balancer.