Skip post-install actions for VNC client installs
...otherwise the VNC client tests fail on aarch64 because we try
to apply the 'console=tty0' workaround for #1661288. Fortunately
we don't really need that for the VNC install test to work, so
let's just skip it. We can make this more sophisticated later if
it turns out to be necessary.
Signed-off-by: Adam Williamson <awilliam@redhat.com>