vg1: Initialize local buffer.

The value in buff[7] will not be initialized when it is checked after
the call to vg1_do_cmd(), if write_cmd_vg() or status_ok() failed.

The bug was found by Gorgone.

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8345 4b0bc96b-bc66-0410-9d44-ebda105a78c1