slow_query: cancel send taskList if ctx is done (#27471)
slow_query: cancel send taskList if ctx is done (#27471)

* slow_query: cancel send taskList if ctx is done

Signed-off-by: tison <b6e578468b915016335bf268450a4dbbe07c0284@gmail.com>
pingcap/tidb,kyle-wang/tidb,c4pt0r/tidb,coocood/tidb,ngaut/tidb,pingcap/tidb,kyle-wang/tidb,coocood/tidb,c4pt0r/tidb,kyle-wang/tidb,kyle-wang/tidb,ngaut/tidb,pingcap/tidb,pingcap/tidb,ngaut/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,pingcap/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,c4pt0r/tidb,kyle-wang/tidb