restore task can't be stoped manually

[foreverneverer]

1、pegasus don‘t provide the tool to stop the “restore_app” task manualy.
2、when try stop it by “drop {app}”，the task still run，but the “query_restore_status” show “restore failed, because some partition's data is damaged on cold backup media”.
3、when restore anther app，the task must wait for the last task to complete，otherwise you'll see that progress is zero.