title: Package destination of restore of .net-core projects is always global package directory
body: <p>We have a solution in which some projects are .net-core projects and some are "normal" .net 4.6.1 projects.
  On solution level we have a NuGet.config-File which sets the repositoryPath:</p>
  
  <pre><code>&lt;configuration&gt;
    &lt;config&gt;
      &lt;add key="repositoryPath" value="packages" /&gt;
    &lt;/config&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>The packages listed in the projects packages.config-Files are getting downloaded into the path specified in Nuget.config -> repositoryPath but the packages specified in the .net-core Project files (via PackageReference) are all downloaded into the global package directory in C:\Users\USERNAME\.nuget\packages.</p>
  
  <p>It doesn't matter if i use Visual Studio 2017 or do it manually via nuget.exe.
  The .net-core projects just ignore the NuGet.config.</p>
  
  <p>What are we doing wrong here?</p>