Ignore discovery-doc download errors (#1047)
Ignore discovery-doc download errors (#1047)

Fixes #1046
chrisdunelm/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,jskeet/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,chrisdunelm/google-api-dotnet-client,googleapis/google-api-dotnet-client,googleapis/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,jskeet/google-api-dotnet-client,Duikmeester/google-api-dotnet-client,googleapis/google-api-dotnet-client,jskeet/google-api-dotnet-client,Duikmeester/google-api-dotnet-client