Failed to download .NET Core tooling 3.1.8

**Repro steps:**

1. Open an ARM template file (azuredeploy.json).
2. .NET Core Tooling output displays

> Downloading .NET Core tooling version(s) 3.1.8 ................ Error!
Failed to download .NET Core tooling 3.1.8:
unable to start ssh-agent service, error :1058
Error connecting to agent: No such file or directory

> Error!
Dotnet Core Acquisition Failed: undefined
3. Report issue

**Extension Version:** 0.1.2
**Error Message:** Dotnet Core Acquisition Failed: undefined
**Error Stack:** Error: Dotnet Core Acquisition Failed: undefined
at c:\Users\anonymous\.vscode\extensions\ms-dotnettools.vscode-dotnet-runtime-0.1.2\dist\extension.js:211:111243
at runMicrotasks ()
at processTicksAndRejections (internal/process/task_queues.js:94:5)

[DotNetAcquisition1600377816739.txt](https://github.com/dotnet/vscode-dotnet-runtime/files/5241990/DotNetAcquisition1600377816739.txt)