vlr: auth_fsm: make sure vsub->auth_fsm = NULL when it terminates

Probably fixes this segfault:

    at ../../../../src/osmo-msc/src/libvlr/vlr_lu_fsm.c:957
    file=file@entry=0x5611d8f10c28 "../../../../src/osmo-msc/src/libvlr/vlr_lu_fsm.c", line=line@entry=1467)
    at ../../../src/libosmocore/src/fsm.c:580
    parent_event_failure=parent_event_failure@entry=6, parent_event_data=parent_event_data@entry=0x0, vlr=0x5611d98862b0,
    msc_conn_ref=msc_conn_ref@entry=0x5611d9aa8150, type=VLR_LU_TYPE_REGULAR, tmsi=4294967295, imsi=0x7ffd756c1cf0 "262423403004874",
    old_lai=0x7ffd756c1ce0, new_lai=0x7ffd756c1ce8, authentication_required=true, ciphering_required=true, is_r99=false, is_utran=false,
    assign_tmsi=true) at ../../../../src/osmo-msc/src/libvlr/vlr_lu_fsm.c:1467
    at ../../../../src/osmo-msc/src/libmsc/gsm_04_08.c:443

The segfault is indirectly caused by 1fbf45c291f7e1f09ef2e862abfeca6a23efdc03,
'enrich context for vlr_subscr_name and ran_conn fi name', which sets auth_fsm
context, on a non-NULL auth_fsm that has been deallocated.

Change-Id: I3c528eed295be2ee673ea295804372f388a0dccd
1 file changed