pacth exist bugfix to master

Author: stuBirdFly

src/main/java/com/alipay/oceanbase/hbase/OHTable.java

@@ -450,8 +450,9 @@ public HTableDescriptor getTableDescriptor() {
      */
     @Override
     public boolean exists(Get get) throws IOException {
-        get.setCheckExistenceOnly(true);
-        return this.get(get).getExists();
+        Get newGet = new Get(get);
+        newGet.setCheckExistenceOnly(true);
+        return this.get(newGet).getExists();
     }
 
     @Override