fix overloaded method matching

this fix contain two parts
1) there was bad return type matching. I found it during testing ruby bindings that benefits from runtime decision about overloaded function
2) second part why it start working is related fix in core that fix function type matching - https://github.com/yast/yast-core/commit/7fb894662dba29389bc553ee3ffdbac9b688826d


Please merge this fix after M2 and M2 with ruby is released because my previous fix in core that fix this issue was wrong but keeps ruby version working.
Thanks