private void addDependsOn(RunImageConfiguration runConfig, List<String> ret) {
        // Only used in custom networks.
        if (runConfig.getNetworkingConfig().isCustomNetwork()) {
            ret.addAll(runConfig.getDependsOn());
        }
    }
Override externalConfiguration when defined via special property.

@param externalConfiguration Map with alternative config
src/main/java/io/fabric8/maven/docker/config/ImageConfiguration.java