Update federation target to etcd/clientv3 (#6119)

With CoreDNS now supporting etcdv3 as the DNS backend, we
can update our federation target to etcdv3. Users will now be
able to use etcdv3 server as the federation backbone.

Minio will update bucket data to etcdv3 and CoreDNS can pick
that data up and serve it as bucket style DNS path.

vendor/github.com/golang/protobuf/proto/equal.go

@@ -109,15 +109,6 @@ func equalStruct(v1, v2 reflect.Value) bool {
 				// set/unset mismatch
 				return false
 			}
-			b1, ok := f1.Interface().(raw)
-			if ok {
-				b2 := f2.Interface().(raw)
-				// RawMessage
-				if !bytes.Equal(b1.Bytes(), b2.Bytes()) {
-					return false
-				}
-				continue
-			}
 			f1, f2 = f1.Elem(), f2.Elem()
 		}
 		if !equalAny(f1, f2, sprop.Prop[i]) {
@@ -146,11 +137,7 @@ func equalStruct(v1, v2 reflect.Value) bool {
 
 	u1 := uf.Bytes()
 	u2 := v2.FieldByName("XXX_unrecognized").Bytes()
-	if !bytes.Equal(u1, u2) {
-		return false
-	}
-
-	return true
+	return bytes.Equal(u1, u2)
 }
 
 // v1 and v2 are known to have the same type.
@@ -261,6 +248,15 @@ func equalExtMap(base reflect.Type, em1, em2 map[int32]Extension) bool {
 
 		m1, m2 := e1.value, e2.value
 
+		if m1 == nil && m2 == nil {
+			// Both have only encoded form.
+			if bytes.Equal(e1.enc, e2.enc) {
+				continue
+			}
+			// The bytes are different, but the extensions might still be
+			// equal. We need to decode them to compare.
+		}
+
 		if m1 != nil && m2 != nil {
 			// Both are unencoded.
 			if !equalAny(reflect.ValueOf(m1), reflect.ValueOf(m2), nil) {
@@ -276,8 +272,12 @@ func equalExtMap(base reflect.Type, em1, em2 map[int32]Extension) bool {
 			desc = m[extNum]
 		}
 		if desc == nil {
+			// If both have only encoded form and the bytes are the same,
+			// it is handled above. We get here when the bytes are different.
+			// We don't know how to decode it, so just compare them as byte
+			// slices.
 			log.Printf("proto: don't know how to compare extension %d of %v", extNum, base)
-			continue
+			return false
 		}
 		var err error
 		if m1 == nil {