Fix relay migration (#964)

* Fix for relay migration on rehandshaking issue. On rehandshake, the relay tunnel doesn't migrate to the new hostinfo object correctly, due to an incorrect Nebula IP sent in the CreateRelayRequest message.
* Add a test for this case

---------

Co-authored-by: Nate Brown <nbrown.us@gmail.com>

connection_manager.go

@@ -231,7 +231,7 @@ func (n *connectionManager) migrateRelayUsed(oldhostinfo, newhostinfo *HostInfo)
 			index = existing.LocalIndex
 			switch r.Type {
 			case TerminalType:
-				relayFrom = newhostinfo.vpnIp
+				relayFrom = n.intf.myVpnIp
 				relayTo = existing.PeerIp
 			case ForwardingType:
 				relayFrom = existing.PeerIp
@@ -256,7 +256,7 @@ func (n *connectionManager) migrateRelayUsed(oldhostinfo, newhostinfo *HostInfo)
 			}
 			switch r.Type {
 			case TerminalType:
-				relayFrom = newhostinfo.vpnIp
+				relayFrom = n.intf.myVpnIp
 				relayTo = r.PeerIp
 			case ForwardingType:
 				relayFrom = r.PeerIp