fix bug for upgrade

session/bootstrap.go

@@ -258,13 +258,14 @@ func bootstrap(s Session) {
 			logutil.Logger(context.Background()).Fatal("check bootstrap error",
 				zap.Error(err))
 		}
+		// For rolling upgrade, we can't do upgrade only in the owner.
+		if b {
+			upgrade(s)
+			return
+		}
 		// To reduce conflict when multiple TiDB-server start at the same time.
 		// Actually only one server need to do the bootstrap. So we chose DDL owner to do this.
 		if dom.DDL().OwnerManager().IsOwner() {
-			if b {
-				upgrade(s)
-				return
-			}
 			doDDLWorks(s)
 			doDMLWorks(s)
 			return