[ricted98]

I encountered an issue in this scenario.

• Some package_links is defined. Let's say .deps/mydep for mydep.
• I use bender clone mydep, then I delete the folder and the override.
• The link now points to a non-existing path, making the symlink broken.
• If I do a bender update mydep I will encounter an error due to the symlink being broken.

I think the issue is that exists follows the symlink pointed path and does not check the actual symlink. This PR should fix the issue.