Avoid harmless warnings due lack of oVirt on build
    
    > remote-viewer.c: In function 'remote_viewer_get_property':
    > remote-viewer.c:227:26: warning: unused variable 'priv' [-Wunused-variable]
    >      RemoteViewerPrivate *priv = self->priv;
    >                           ^~~~
    > remote-viewer.c:224:36: warning: unused parameter 'value' [-Wunused-parameter]
    >      GValue *value, GParamSpec *pspec)
    >              ^~~~~
    > virt-viewer-window.c: In function 'virt_viewer_window_menu_change_cd_activate':
    > virt-viewer-window.c:1077:62: warning: unused parameter 'self' [-Wunused-parameter]
    >      VirtViewerWindow *self)
    >                        ^~~~
    
    Signed-off-by: Victor Toso <victortoso@redhat.com>