libvlr: fix auth_fsm_term(): use proper value-string for cause

Change-Id: Ia0868dce2da5cb78c30cf518870c3d91144499b9
diff --git a/tests/msc_vlr/msc_vlr_test_gsm_authen.err b/tests/msc_vlr/msc_vlr_test_gsm_authen.err
index 6317820..94c1694 100644
--- a/tests/msc_vlr/msc_vlr_test_gsm_authen.err
+++ b/tests/msc_vlr/msc_vlr_test_gsm_authen.err
@@ -3271,7 +3271,7 @@
 DVLR VLR_Authenticate(IMSI-901700000004620:GERAN-A:LU){VLR_SUB_AS_WAIT_RESP}: Received Event VLR_AUTH_E_MS_AUTH_RESP
 DVLR SUBSCR(IMSI-901700000004620) AUTH on GERAN received SRES/RES:  (0 bytes)
 DVLR SUBSCR(IMSI-901700000004620) AUTH SRES/RES missing
-DVLR VLR_Authenticate(IMSI-901700000004620:GERAN-A:LU){VLR_SUB_AS_WAIT_RESP}: Authentication terminating with result FAILURE, cause Illegal MS
+DVLR VLR_Authenticate(IMSI-901700000004620:GERAN-A:LU){VLR_SUB_AS_WAIT_RESP}: Authentication terminating with result FAILURE, cause ILLEGAL_MS
 DVLR VLR_Authenticate(IMSI-901700000004620:GERAN-A:LU){VLR_SUB_AS_WAIT_RESP}: state_chg to VLR_SUB_AS_AUTH_FAILED
 GSUP --> HLR: OSMO_GSUP_MSGT_AUTH_FAIL_REPORT: 0b010809710000004026f00a0101
 DVLR VLR_Authenticate(IMSI-901700000004620:GERAN-A:LU){VLR_SUB_AS_AUTH_FAILED}: Terminating (cause = OSMO_FSM_TERM_REGULAR)