added svn args for info when getting current revision

When svn_args_info is present in the subversion resource in a recipe, i.e.

```ruby
subversion "MyApp" do
  repository "http://some.svn.com/trunk/"
  revision "HEAD"
  destination "/opt/mysources/couch"
  svn_arguments '--config-dir /etc/subversion/'
  svn_info_args '--config-dir /etc/subversion/'
  action :sync
end
```

Running will fail because the svn info command issued by find_current_revision doesn't include the arguments.
In my case it was because I was using a system user for the checkout and the command was returning:
```
---- Begin output of  ----
STDOUT:
STDERR: svn: warning: W000013: Can't open file '/root/.subversion/servers': Permission denied
---- End output of  ----
```

The PR adds any arguments that are passed to that instance of svn info as well.
I don't think we should be setting this in the before block.  Setting the info_args here means that ALL examples in the `context "determining the revision of the currently deployed code" do` block will be using those same info args.  What you really want is 1 test that sets these args and then validates them.

I think you should duplicate the `it "sets the revision to nil if there isn't any deployed code yet" do` and set your `@resource.svn_info_args` only in that new test.  Make sense?

There are fancier ways to accomplish this (like `shared_examples`) but since this spec file is pretty small the easiest thing is to just add a new test.  Unless you would like to learn the fancy way to handle this?