SMS-over-GSUP: set Source Name IE for *all* messages

We do include this IE in result and error messages, but somehow
not in the request messages.  For the sake of consistency, let's
ensure that the Source Name IE is present in all SMS related PDUs.

This additionally brings osmo-msc in sync with ttcn3-msc-test, which
was modified to expect the Source Name IE in all receive templates,
and makes the following testcases pass [again]:

* MSC_Tests.TC_gsup_mo_sms
* MSC_Tests.TC_gsup_mo_smma
* MSC_Tests.TC_gsup_mo_mt_sms_rp_mr

Change-Id: I65f5e3b7a0688e258979bb2679598659881a4321
Related: osmo-ttcn3-hacks.git Ic24d3082fe3dce08e43e8f3ecb6d6132503c55c6
Related: OS#6135
diff --git a/src/libmsc/gsm_04_11_gsup.c b/src/libmsc/gsm_04_11_gsup.c
index d1c2f27..1afdfab 100644
--- a/src/libmsc/gsm_04_11_gsup.c
+++ b/src/libmsc/gsm_04_11_gsup.c
@@ -98,6 +98,7 @@
 	gsup_msg.sm_rp_ui_len = msgb_l4len(msg);
 	gsup_msg.sm_rp_ui = (uint8_t *) msgb_sms(msg);
 
+	gsup_client_mux_tx_set_source(trans->net->gcm, &gsup_msg);
 	return gsup_client_mux_tx(trans->net->gcm, &gsup_msg);
 }
 
@@ -120,6 +121,7 @@
 	/* Indicate SMMA as the Alert Reason */
 	gsup_msg.sm_alert_rsn = OSMO_GSUP_SMS_SM_ALERT_RSN_MEM_AVAIL;
 
+	gsup_client_mux_tx_set_source(trans->net->gcm, &gsup_msg);
 	return gsup_client_mux_tx(trans->net->gcm, &gsup_msg);
 }