Set grpc :authority header from request header (#8912)

This is to fix that the `:authority` header is  set to `upstream_balancer`

rootfs/etc/nginx/template/nginx.tmpl

@@ -1388,13 +1388,11 @@ stream {
             {{ end }}
 
             {{/* By default use vhost as Host to upstream, but allow overrides */}}
-            {{ if not (eq $proxySetHeader "grpc_set_header") }}
             {{ if not (empty $location.UpstreamVhost) }}
             {{ $proxySetHeader }} Host                   {{ $location.UpstreamVhost | quote }};
             {{ else }}
             {{ $proxySetHeader }} Host                   $best_http_host;
             {{ end }}
-            {{ end }}
 
             # Pass the extracted client certificate to the backend
             {{ if not (empty $server.CertificateAuth.CAFileName) }}

test/e2e/annotations/grpc.go

@@ -120,6 +120,7 @@ var _ = framework.DescribeAnnotation("backend-protocol - GRPC", func() {
 
 		metadata := res.GetMetadata()
 		assert.Equal(ginkgo.GinkgoT(), metadata["content-type"].Values[0], "application/grpc")
+		assert.Equal(ginkgo.GinkgoT(), metadata[":authority"].Values[0], host)
 	})
 
 	ginkgo.It("authorization metadata should be overwritten by external auth response headers", func() {