security/softether-devel: make LogFileList command[1] work

properly as well as r512198. Also config backup function should work now.

[1] https://www.softether.org/4-docs/1-manual/6._Command_Line_Management_Utility_Manual/6.3_VPN_Server_%2F%2F_VPN_Bridge_Management_Command_Reference_(For_Entire_Server)#6.3.55_.22LogFileList.22:_Get_List_of_Log_Files

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