Add specs for Rex::OLE::Util and Rex::OLE::CLSID

Verification steps

- [ ] Be sure which travis is green
- [ ] Run the specs locally and ensure all the tests pass

```
$ rspec spec/lib/rex/ole/*
Rex::OLE::Util ..........................................
Rex::OLE::CLSID ......

Finished in 0.0584 seconds
48 examples, 0 failures

```