SRAMP-408 Tab completion no longer works in s-ramp CLI

https://issues.jboss.org/browse/SRAMP-408

Take a look to the last file, FileNameCompleter. The code that was there, was previously working or not working... xD 

I couldn't check on Windows, but I imagine it will work. The problem was that there was an iteration over a List and in the loop also was getting modified the iterated object. With the code I added I imagine will work.