fix span serialize bug.

skywalking-commons/skywalking-trace/src/main/java/com/a/eye/skywalking/trace/Span.java

@@ -270,6 +270,7 @@ public class Span implements ISerializable<SpanMessage> {
     public SpanMessage serialize() {
         SpanMessage.Builder builder = SpanMessage.newBuilder();
         builder.setSpanId(spanId);
+        builder.setParentSpanId(parentSpanId);
         builder.setStartTime(startTime);
         builder.setEndTime(endTime);
         builder.setOperationName(operationName);
@@ -292,6 +293,7 @@ public class Span implements ISerializable<SpanMessage> {
     @Override
     public void deserialize(SpanMessage message) {
         spanId = message.getSpanId();
+        parentSpanId = message.getParentSpanId();
         startTime = message.getStartTime();
         endTime = message.getEndTime();
         operationName = message.getOperationName();

skywalking-commons/skywalking-trace/src/main/proto/trace.proto

@@ -22,11 +22,12 @@ message SegmentRefMessage {
 
 message SpanMessage {
     int32 spanId = 1;
-    int64 startTime = 2;
-    int64 endTime = 3;
-    string operationName = 4;
-    repeated KeyValue tags = 5;
-    repeated LogDataMessage logs = 6;
+    int32 parentSpanId = 2;
+    int64 startTime = 3;
+    int64 endTime = 4;
+    string operationName = 5;
+    repeated KeyValue tags = 6;
+    repeated LogDataMessage logs = 7;
 }
 
 message LogDataMessage {