store gsup peer upon accepting LU

Store the GSUP client's IPA_IDTAG_SERNR in vlr_number or sgsn_number (depending
on is_ps), just before sending the Insert Subscriber Data message after a
successful LU Req. Log about it.

Original patch: Ib2611421f3638eadc361787af801fffe9a34bd8a by laforge
Related: OS#2796

Change-Id: If438664faa5d68404f465f8b2002c6d03bbf3ceb
1 file changed