rx_delay is meaningful to have as the default, as that is RU-model
specific and goes as T2a+T3a-Toffset.

tx_delay is less meaningful to have as the default: it is T12 + T2a,
where T2a is RU-model specific and T12 depends on the length of the
fiber link. But I keep the previous default because it might be handy to
have something as the default.

Also restore previous values for sunwave n_antenna_* as it was there in
old ors-amarisoft SR.