private void addSources(ConfigSourceSet sourceSet) {
        this.sourceSet = sourceSet;
        synchronized (connections) {
            for (String address : sourceSet.getSources()) {
                connections.put(address, new JRTConnection(address, supervisor));
            }
        }
        currentConnection = initialize();
    }
A pool of JRT connections to a config source (either a config server or a config proxy).
The current connection is chosen randomly when calling {@link #switchConnection(Connection)}
(it will continue to use the same connection if there is only one source).
The current connection is available with {@link #getCurrent()}.

@author Gunnar Gauslaa Bergem
@author hmusum
config/src/main/java/com/yahoo/vespa/config/JRTConnectionPool.java