Official build broken restoring internal tools

[jaredpar]

The change to restore our internal tools appears to have broken the official builds. Post merge they are failing with the following error:

Build started 1/25/2020 4:09:22 PM.
     1>Project "F:\workspace\_work\1\s\eng\common\internal\Tools.csproj" on node 1 (Restore target(s)).
     1>Restore:
         Restoring packages for F:\workspace\_work\1\s\eng\common\internal\Tools.csproj...
     1>C:\Program Files\dotnet\sdk\3.0.100\NuGet.targets(123,5): error : Problem starting the plugin 'C:\Users\vsagent\.nuget\plugins\netcore\CredentialProvider.Microsoft\CredentialProvider.Microsoft.dll'. Plugin 'CredentialProvider.Microsoft' failed within 5.570 seconds with exit code -1. [F:\workspace\_work\1\s\eng\common\internal\Tools.csproj]
     1>C:\Program Files\dotnet\sdk\3.0.100\NuGet.targets(123,5): error : Unable to load the service index for source https://devdiv.pkgs.visualstudio.com/_packaging/dotnet-core-internal-tooling/nuget/v3/index.json. [F:\workspace\_work\1\s\eng\common\internal\Tools.csproj]
C:\Program Files\dotnet\sdk\3.0.100\NuGet.targets(123,5): error :   Response status code does not indicate success: 401 (Unauthorized). [F:\workspace\_work\1\s\eng\common\internal\Tools.csproj]
     1>Done Building Project "F:\workspace\_work\1\s\eng\common\internal\Tools.csproj" (Restore target(s)) -- FAILED.

PR that appears to have broken this #1846

Builds

• https://dev.azure.com/dnceng/internal/_build/results?buildId=496808
• https://dev.azure.com/dnceng/internal/_build/results?buildId=497020

[safern]

I can confirm this is correctly fixed, we haven't hit this since my last fix went in.