Fix Dockerfile used to regenerate gRPC golang code

[jodh-intel]

The Dockerfile used to regenerate the protocol buffer golang code currently:

• Fails to install golang

  Reason: URL incorrect:

  	url
  incorrect	https://storage.googleapis.com/golang/go${GO_VERSION}.linux-$(arch).tar.gz
  correct	https://storage.googleapis.com/golang/go${GO_VERSION}.linux-${arch}.tar.gz

• fails to run ./hack/update-generated-agent-proto.sh
  Reason: That script now uses https://github.com/gogo/protobuf/tree/master/protoc-gen-gogofast rather than https://github.com/golang/protobuf/protoc-gen-go.

It's also unclear to me why we're pinning the tool versions in Dockerfile to specific versions of the protobuf tooling?

[jshachm]

@jodh-intel
Different version of protobuf tools may generate different codes
As you can see in #222 .When I use different version, I got different result.

[devimc]

Closing issue, I couldn't reproduce this issue, please feel free to reopen it if you face this issue it again