Adding a reference adds an absolute hintpath

Reported through VS Feedback - https://developercommunity.visualstudio.com/content/problem/14754/in-vs2017-rc-problem-adding-references-to-the-new.html

When one adds a reference to a external dll it adds it like this:

```xml


C:\Users\myname.nuget\packages\system.runtime.serialization.primitives\4.1.1\ref\netstandard1.3\System.Runtime.Serialization.Primitives.dll


C:\Users\myname.nuget\packages\system.xml.xmlserializer\4.3.0\ref\netstandard1.3\System.Xml.XmlSerializer.dll

```
This will not work in a team environment, or in a continious build envirenment.
It only works for me on my machine.