Read oVirt CA and pass it to gtk-vnc

The connection file created by oVirt contains the trusted CA. When https://gitlab.gnome.org/GNOME/gtk-vnc/-/merge_requests/24 is merged, we can pass this CA certificate to gtk-vnc to have it trusted. This can replace manually putting the cacert.pem into ~/.pki/CA/

Signed-off-by: Jean-Louis Dupond jean-louis@dupond.be