We're gonna drop support for non-systemd init scripts soon,
and we don't want Travis CI builds to break when we do.

Since we have init system auto-detection, we can just rely on
that and stop passing --with-init-script to configure entirely.
Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>