While testing the OAI 5G RAN in SA mode, it appears that the PDU session
establishment request is using the wrong security header type.

The current used header is: "Integrity protected and ciphered with new
5G NAS security context".

However, according to TS 24.501, Table 9.3.1, this header can only be used
by the "Security mode complete" procedure.

Changes:

 - Hence, the new security header has been changed to "Integrity protected
   and ciphered", which will use the security context generated during the
   "Security mode complete".

 - Sequences numbers and NAS counters have been updated to reflect that
   change.