Fix C# Dockerfiles

templates/tools/dockerfile/csharp_deps.include

tools/dockerfile/interoptest/grpc_interop_csharp/Dockerfile

...kerfile/interoptest/grpc_interop_csharpcoreclr/Dockerfile

...kerfile/stress_test/grpc_interop_stress_csharp/Dockerfile

tools/dockerfile/test/csharp_coreclr_x64/Dockerfile

tools/dockerfile/test/csharp_jessie_x64/Dockerfile

tools/dockerfile/test/multilang_jessie_x64/Dockerfile