message: Update protobuf to 3.6.1.1
  protobuf 3.6.1.1 contains a fix for protobuf bzl file. This will fix TF Windows build with Bazel@HEAD, allowing us to test TensorFlow in downstream.
diff: @@ -347,11 +347,11 @@ def tf_workspace(path_prefix = "", tf_repo_name = ""):
  )
  PROTOBUF_URLS = [
  - "https://mirror.bazel.build/github.com/google/protobuf/archive/v3.6.1.tar.gz",
  - "https://github.com/google/protobuf/archive/v3.6.1.tar.gz",
  + "https://mirror.bazel.build/github.com/google/protobuf/archive/v3.6.1.1.tar.gz",
  + "https://github.com/google/protobuf/archive/v3.6.1.1.tar.gz",
  ]
  - PROTOBUF_SHA256 = "3d4e589d81b2006ca603c1ab712c9715a76227293032d05b26fca603f90b3f5b"
  - PROTOBUF_STRIP_PREFIX = "protobuf-3.6.1"
  + PROTOBUF_SHA256 = "1ade182f91f0fa6c6116195def5d22270e01b9d03fe91319e4c6215022d0d24b"
  + PROTOBUF_STRIP_PREFIX = "protobuf-3.6.1.1"
  tf_http_archive(
  name = "protobuf_archive",
  