sgsn_test: Fix wrong definition of wrap func

Commit 058cd573d8 added 2 new pointer parameters to
gprs_subscr_request_auth_info, but forgot to update wraps of the
function in sgsn_test.

I catched this today because openbsc build test sgsn_test was failing.
Closed look up to the logs showed:
Assert failed (auts != NULL) == (auts_rand != NULL) openbsc/openbsc/src/gprs/gprs_subscriber.c:791

Change-Id: Ie9e4af6da0339536fb20ca0b7bbcf6f485bd522c
1 file changed