Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/google.golang.org/grpc/status/go16.go

@@ -0,0 +1,42 @@
+// +build go1.6,!go1.7
+
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package status
+
+import (
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/codes"
+)
+
+// FromContextError converts a context error into a Status.  It returns a
+// Status with codes.OK if err is nil, or a Status with codes.Unknown if err is
+// non-nil and not a context error.
+func FromContextError(err error) *Status {
+	switch err {
+	case nil:
+		return New(codes.OK, "")
+	case context.DeadlineExceeded:
+		return New(codes.DeadlineExceeded, err.Error())
+	case context.Canceled:
+		return New(codes.Canceled, err.Error())
+	default:
+		return New(codes.Unknown, err.Error())
+	}
+}