CHEF-5316: Constantly update owner/group in the resource of link

In the link resource, group / owner associated will be **constantly updated** in the following cases.

* target_file is already exists.
* target_file owner or group associated is the same before executing chef resources
* a to file doesn't exist

Hope to cover to checking the permissions symbolic link in this case :grin:

**Execute examples**

resource code:

```ruby
# recipes/xxx.rb

link "/tmp/fofile-link" do
  link_type :symbolic
  to "/tmp/fofile"
  owner 501
  group 501
  action :create
end
```

symlink is exists but to file doesn't exist.

```sh
$ ls -n1 /tmp/
lrwxrwxrwx 1 501 501 11 May 20 22:12 fofile-link -> /tmp/fofile
```

Chef exec result:

```
Starting Chef Client, version 11.12.4
Compiling Cookbooks...
...

* link[uploads] action create
  - Would change owner from '' to '501'  # => from is empty !
  - Would change group from '' to '501'  # => from is empty !
```

---

[commit diff --ignore-space-change](https://github.com/opscode/chef/pull/1447/files?w=1) (with param `?w=1`)