Admiller/oo exec ruby

I updated oo-exec-ruby to handle multiple versions of ruby, this should work for all scenarios that I believe us to support. I also changed oo-mco since that invocation of oo-exec-ruby seemed unnecessary because it relies upon RHSCL ruby193 anyways.

@sosiouxme @detiber - please review

[test]
Any reason to not use oo-exec-ruby here? I don't know of a scl-in-scl bug that would bite us with oo-mco, but would be best to avoid the possibility, I think.