Update tos_task.c fix a bug

[Jer6y]

修复 tos_task_create_dy 的一处临界区问题的BUG

[tencent-adm]

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[Supowang1989]

很好，确实存在这个极端情况，高任务一直占用CPU，导致无法删除自己。不过我们cr代码,有一些修改建议，辛苦重新pr，commit信息在补齐函数名称哈