transport/client: Return Unknown on missing or unparsable grpc-status (grpc#8702)

See https://github.com/grpc/grpc/blob/master/doc/statuscodes.md for more
details.

RELEASE NOTES:
* transport/client : Return Unknown on missing or unparsable
grpc-status.

Author: mbissa

internal/transport/http2_client.go

@@ -1464,7 +1464,7 @@ func (t *http2Client) operateHeaders(frame *http2.MetaHeadersFrame) {
 		recvCompress   string
 		httpStatusErr  string
 		// the code from the grpc-status header, if present
-		grpcStatusCode = codes.Internal
+		grpcStatusCode = codes.Unknown
 		// headerError is set if an error is encountered while parsing the headers
 		headerError string
 		httpStatus  string

internal/transport/transport_test.go

@@ -2794,7 +2794,7 @@ func (s) TestClientDecodeTrailer(t *testing.T) {
 					{Name: ":status", Value: "xxxx"},
 				},
 			},
-			wantEndStreamStatus: status.New(codes.Internal, ""),
+			wantEndStreamStatus: status.New(codes.Unknown, ""),
 		},
 		{
 			name: "http2_frame_size_exceeds",
@@ -2813,7 +2813,7 @@ func (s) TestClientDecodeTrailer(t *testing.T) {
 					{Name: "content-type", Value: "application/grpc"},
 				},
 			},
-			wantEndStreamStatus: status.New(codes.Internal, ""),
+			wantEndStreamStatus: status.New(codes.Unknown, ""),
 		},
 		{
 			name: "deadline_exceeded_status",

test/http_header_end2end_test.go

@@ -169,7 +169,7 @@ func (s) TestHTTPHeaderFrameErrorHandlingNormalTrailer(t *testing.T) {
 				// trailer missing grpc-status
 				":status", "502",
 			},
-			errCode: codes.Internal,
+			errCode: codes.Unknown,
 		},
 		{
 			name: "malformed grpc-status-details-bin field with status 404 to be ignored due to content type",