try installing nuget

Author: vslee

azure-pipelines.yml

@@ -75,6 +75,7 @@ jobs:
           packagesToPack: 'src/ExchangeSharp/ExchangeSharp.csproj'
           packDestination: '$(Build.ArtifactStagingDirectory)'
           versioningScheme: off
+      - task: NuGetToolInstaller@1
       - task: NuGetAuthenticate@0
         displayName: 'NuGet Authenticate'
       #- script: nuget push $(Build.ArtifactStagingDirectory)/*.nupkg -NonInteractive -Source https://pkgs.dev.azure.com/DigitalRuby/DigitalRuby/_packaging/DigitalRuby/nuget/v3/index.json -ApiKey AzureArtifacts -Verbosity Detailed