gprs_ns2_sns: bss: set gss->family

gss->family (and gss->ip) was never set.
So IPv6 should have never worked.

Fixes: e769f5226be6 ("gprs_ns2_sns: rework IP-SNS initial remote")
Related: OS#5036
Change-Id: I4e39dc5c7f766a7040645ceb62afdf6a9cfad00f
diff --git a/src/gb/gprs_ns2_sns.c b/src/gb/gprs_ns2_sns.c
index 3f09054..367f77c 100644
--- a/src/gb/gprs_ns2_sns.c
+++ b/src/gb/gprs_ns2_sns.c
@@ -1600,6 +1600,7 @@
 			gss->initial = llist_entry(gss->initial->list.next, struct sns_endpoint, list);
 		}
 
+		gss->family = gss->initial->saddr.u.sa.sa_family;
 		gss->reselection_running = false;
 		osmo_fsm_inst_state_chg(fi, GPRS_SNS_ST_BSS_SIZE, nse->nsi->timeout[NS_TOUT_TSNS_PROV], 1);
 		break;