As seen in a running osmo-msc:
"vlr_access_req_fsm.c:153
msc_a(IMSI-....:MSISDN-...:TMSI-0x...:GERAN-A-8:CM_SERVICE_REQ){MSC_A_ST_RELEASING}:
Event MSC_A_EV_CN_CLOSE not permitted"
Also seen in several unit tests, which need update.
The action event handler for that state is actually already
expecting/handling the event by ignoring it, so we should allow it.
Change-Id: I4d30cffab693529aab3ba736419dec116a4dd7ef