Version Used:
VS15.4

Steps to Reproduce:

1. Create an empty solution
2. Create a project named A with <TargetFrameworks>net46;netstandard1.0</TargetFrameworks>
3. Create project named B with <TargetFrameworks>net46;netstandard2.0</TargetFrameworks>
4. Make the B project reference A
5. With Roslyn workspace APIs do the following:

var props = new Dictionary<string, string>() { { "TargetFramework", "netstandard2.0" } };
var ws = MSBuildWorkspace.Create(props);
var project = await ws.OpenProjectAsync("B.csproj");

Expected Behavior:
The project.MetadataReferences member contains valid references.

Actual Behavior:
The project.MetadataReferences member is empty.

The loaded project B will be in a inconsistent state, as MSBuildWorkspace will try to load the A project using netstandard2.0, which it does not support.