Send integrity protected NAS Registration Request when UE has a valid current 5G NAS security context

• Send integrity protected NAS Registration Request when NAS UE has a valid current 5G NAS security context according to 4.4.2.5 TS 24.501:

when a UE in 5GMM-IDLE mode establishes a new NAS signalling connection and has a valid current 5G NAS security context, the UE shall transmit > the initial NAS message integrity protected with the current 5G NAS security context and further protect this message as specified in subclause 4.4.6. -> handled in !3176 (merged)