This should use an array of strings to pass into `shell_out` rather than constructing a string which will cause things to be interpreted by a shell which means we will have to quote '*':

```ruby
def run_rs_tag_util(*args)
  assert_rightscale
  cmd = ['rs_tag'] + args
  ...
end
```

Also, this means the `'--list'` argument should be made explicit where it is called.