A cache can send a 'NO_DATA_AVAILABLE' error during version negotiation

A cache can send a 'NO_DATA_AVAILABLE' error during version negotiation
so handle this case as well. This error triggers an RTR_EVNT_NO_DATA
event that moves the session to RTR_STATE_ESTABLISHED (and out of negotiation).

When there is no data available the session_id remains unset until data
becomes available. So handle this case not only in rtr_parse_cache_response()
but also in rtr_parse_notify().

RTR_EVNT_NO_DATA arms the RTR_EVNT_TIMER_RETRY timer. On expiry send a
reset or serial query depending on the cache session state.

OK tb@