Commented out poll_fd and file watcher tests due to open issues 3015, 3016 and 3020

https://github.com/JuliaLang/julia/issues/3015
https://github.com/JuliaLang/julia/issues/3016
https://github.com/JuliaLang/julia/issues/3020

 The above bug result in the tests failing in a non-predictable manner. Besides the the API and implementation will undergo large changes in the context of  https://github.com/JuliaLang/julia/issues/3020