Merge pull request #4787 from jtattermusch/upgrade_protobuf_beta2

src/compiler/csharp_generator.cc

src/csharp/Grpc.Examples.Tests/Grpc.Examples.Tests.csproj

src/csharp/Grpc.Examples.Tests/packages.config

src/csharp/Grpc.Examples/Grpc.Examples.csproj

src/csharp/Grpc.Examples/Math.cs

src/csharp/Grpc.Examples/MathGrpc.cs

src/csharp/Grpc.Examples/packages.config

...harp/Grpc.HealthCheck.Tests/Grpc.HealthCheck.Tests.csproj

src/csharp/Grpc.HealthCheck.Tests/packages.config

src/csharp/Grpc.HealthCheck/Grpc.HealthCheck.csproj

src/csharp/Grpc.HealthCheck/Health.cs

src/csharp/Grpc.HealthCheck/HealthGrpc.cs

src/csharp/Grpc.HealthCheck/packages.config

src/csharp/Grpc.IntegrationTesting/Control.cs

src/csharp/Grpc.IntegrationTesting/Empty.cs

...rp/Grpc.IntegrationTesting/Grpc.IntegrationTesting.csproj

src/csharp/Grpc.IntegrationTesting/Messages.cs

src/csharp/Grpc.IntegrationTesting/Payloads.cs

src/csharp/Grpc.IntegrationTesting/Services.cs

src/csharp/Grpc.IntegrationTesting/ServicesGrpc.cs