bsc: Add API to mock BSC RSL IP addr

Change-Id: I9ca67964e656943b50967a27a88054fd3e484672
diff --git a/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl b/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
index 71b44cf..814cf97 100644
--- a/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
+++ b/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
@@ -52,6 +52,9 @@
   channel allocator ascending
   rach tx integer 9
   rach max transmission 7
+% if bsc.net.get('rsl_ip', False):
+  ip.access rsl-ip ${bsc.net.rsl_ip}
+% endif
   ip.access unit_id ${bts.ipa_unit_id} 0
   oml ip.access stream_id ${bts.stream_id} line 0
 % if bts.get('sgsn', False):