Don't lose the stack when rethrowing exceptions from TestHost

[dfederm]

I'm seeing the following when trying to run vstest:

Microsoft (R) Test Execution Command Line Tool Version 15.5.0-dev
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
Testhost process exited with error: Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'System.Threading.Thread, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
   at Microsoft.VisualStudio.TestPlatform.TestHost.Program.Main(String[] args)

The strack trace for the exception is lost since it's not re-thrown properly.

[msftclas]

@dfederm,
Thanks for your contribution as a Microsoft full-time employee or intern. You do not need to sign a CLA.
Thanks,
Microsoft Pull Request Bot

[smadala]

@dotnet-bot Please test Windows_NT / Debug Build .

[singhsarab]

Thanks.