fix detect exitepoch at first time
fix detect exitepoch at first time

kod3r/taskgraph,plutoshe/taskgraph,go-distributed/meritop,taskgraph/taskgraph,taskgraph/taskgraph,BaiGang/taskgraph,5kg/taskgraph,dzch/taskgraph,plutoshe/taskgraph,fengjingchao/taskgraph,fengjingchao/taskgraph,plutoshe/mapreduceOfTaskgraph,go-distributed/meritop,kod3r/taskgraph,5kg/taskgraph,BaiGang/taskgraph,plutoshe/mapreduceOfTaskgraph,dzch/taskgraph