log which DTAP messages are sent to RAN

So far, the logging said only "RAN encode: BSSMAP: DTAP", but not *which* DTAP
message, which is in fact a very interesting detail when reading osmo-msc logs.

Change-Id: I0cb8d1e3307737ffe53730c64bb984adacedb2da
diff --git a/tests/msc_vlr/msc_vlr_test_rest.err b/tests/msc_vlr/msc_vlr_test_rest.err
index fb10e6a..4121a26 100644
--- a/tests/msc_vlr/msc_vlr_test_rest.err
+++ b/tests/msc_vlr/msc_vlr_test_rest.err
@@ -435,6 +435,7 @@
 DREF VLR subscr TMSI-0x23422342 - _lu_fsm_associate_vsub: now used by 1 (active-conn)
 DVLR vlr_lu_fsm(TMSI-0x23422342:GERAN-A:LU){VLR_ULA_S_IDLE}: vlr_loc_upd_want_imsi()
 DVLR vlr_lu_fsm(TMSI-0x23422342:GERAN-A:LU){VLR_ULA_S_IDLE}: state_chg to VLR_ULA_S_WAIT_IMSI
+DBSSAP msc_a(TMSI-0x23422342:GERAN-A:LU){MSC_A_ST_AUTH_CIPH}: Sending DTAP: MM GSM48_MT_MM_ID_REQ
 DMSC msc_a(TMSI-0x23422342:GERAN-A:LU){MSC_A_ST_AUTH_CIPH}: RAN encode: DTAP on GERAN-A
 - DTAP --GERAN-A--> MS: GSM48_MT_MM_ID_REQ: 051801
 - DTAP matches expected message