[improve][broker]Use cursor.isActive instead to judge if cursor is ac…

…tive (apache#19159)

Co-authored-by: gavingaozhangmin <gavingaozhangmin@didiglobal.com>

managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedLedgerImpl.java

@@ -3663,7 +3663,7 @@ Pair<PositionImpl, Long> getFirstPositionAndCounter() {
 
     public void activateCursor(ManagedCursor cursor) {
         synchronized (activeCursors) {
-            if (activeCursors.get(cursor.getName()) == null) {
+            if (!cursor.isActive()) {
                 Position positionForOrdering = config.isCacheEvictionByMarkDeletedPosition()
                         ? cursor.getMarkDeletedPosition()
                         : cursor.getReadPosition();