The new spec uses existing EchoDuplicate service in
grpc.testing.duplicate, which refers grpc.testing.Empty,
and verifies if the plugin generates this correctly as
Grpc::Testing::Empty.

The encoding of the issuer field in this cert is now a PRINTABLESTRING
as opposed to UTF8STRING in the previous server1.pem which was causing
the Go issue.

Fixes #4086.

- provides a noop logger unless the user explicit adds a logging method
  to the GRPC namespace