Revert "display-vnc: fix zoom-level set by command line"
    
    This reverts commit 68148e1bd1a47ff370c78e2569a57ae0f3d8a400.
    
    The commit in question was causing a regression about a tiny window
    being displayed when opening a vnc guest.
    The issue only happens with the gtk2 version of virt-viewer.
    
    rhbz#1170071 that was solved by the reverted commit is avoided by
    the commit c45a30e909656434aa842d48d828ef038ec7364a.
    
    Resolves: rhbz#1201679