update PLC status after initialization

This is necessary especially if existed PLC program is loaded, but PLC
is not started automatically. In this case taskbar icon shows that PLC
isn't empty.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType>
    <Linux/>
  </TargetType>
</BeremizRoot>