[bug fix]weed daemon exit due to hangup signal when terminal close
[bug fix]weed daemon exit due to hangup signal when terminal close

k85169336/seaweedfs,hxiaodon/seaweedfs,chrislusf/seaweedfs,chrislusf/seaweedfs,k85169336/seaweedfs,chrislusf/seaweedfs,chrislusf/seaweedfs,hxiaodon/seaweedfs