sgsn: Don't send Attach Accept if initial LU is rejected

This should fix TTCN3, SGSN_Tests.TC_attach_gsup_lu_reject, wher eit can
be seen that before this patch SGSN sent Attach Accept before
sending/receing the first LU (so if LU was rejected by HLR, then attach
was already accepted).
Similary, it also fixes SGSN_Tests.TC_attach_gsup_lu_reject.

Change-Id: Ie3970a790cf2b674da4d9e23a83c4a65d27d5de4
4 files changed