RSL_Emulation: Fail explicitly on ASP_IPA_EVENT_DOWN

Otherwise RSL layer fails this way when this event is received:

RSL_Emulation.ttcn:429 Receive operation on port IPA_PT succeeded, message from TC_chan_act_a51-RSL-IPA(3): @IPA_Emulation.ASP_IPA_Event: { up_down := ASP_IPA_EVENT_DOWN (0) } id 9
- Function main_client was stopped. PTC terminates.
RSL_Emulation.ttcn:429 Message with id 9 was extracted from the queue of IPA_PT.
RSL_Emulation.ttcn:430 setverdict(fail): none -> fail reason: "Received unknown primitive from IPA", new component reason: "Received unknown primitive from IPA"

We now fail with a clearer message "Lost IPA connection!". These
failures seem to happen under high load when the BTS doesn't get a
steady clock from osmo-trx.

Change-Id: Idc6565c9de72d98015d56a41e5616c46051c8a8d
1 file changed