Try really hard (Azure#25852)

eng/pipelines/templates/steps/install-dotnet.yml

@@ -11,20 +11,23 @@ steps:
   # Installation steps need to be uncommented when switching to a newer SDK that's not available on DevOps agents
   - task: UseDotNet@2
     displayName: 'Use .NET Core SDK'
+    retryCountOnTaskFailure: 3
     inputs:
       useGlobalJson: true
       performMultiLevelLookup: true
   # test-proxy requires ASP.NET Core 5.0 runtime
   - task: UseDotNet@2
     condition: and(succeeded(), ne(variables['Agent.OS'], 'Windows_NT')) # Windows supports MultiLevelLookup and doesn't need explicit framework installation
     displayName: 'Use .NET Core 5.0 SDK'
+    retryCountOnTaskFailure: 3
     inputs:
       packageType: sdk
       performMultiLevelLookup: true
       version: "5.0.x"
   - task: UseDotNet@2
     condition: and(succeeded(), ne(variables['Agent.OS'], 'Windows_NT')) # Windows supports MultiLevelLookup and doesn't need explicit framework installation
     displayName: 'Use .NET Core 3.1 SDK'
+    retryCountOnTaskFailure: 3
     inputs:
       # AspNetCore runtime pack can't be installed outside of SDK and we need it for intergation tests
       packageType: sdk