Fixed usage of metadata context
Fixed usage of metadata context

improbable-eng/grpc-web,MarcusLongmuir/grpc-web,improbable-eng/grpc-web,MarcusLongmuir/grpc-web,MarcusLongmuir/grpc-web,improbable-eng/grpc-web,MarcusLongmuir/grpc-web,improbable-eng/grpc-web,MarcusLongmuir/grpc-web,improbable-eng/grpc-web