tests: voice: Add voice call test with Osmux enabled

Change-Id: Ie4f360a77f6fcbc74f140a7fcb5feef2d94ac734
diff --git a/src/osmo_gsm_tester/templates/osmo-mgw.cfg.tmpl b/src/osmo_gsm_tester/templates/osmo-mgw.cfg.tmpl
index f91ab30..5f351a4 100644
--- a/src/osmo_gsm_tester/templates/osmo-mgw.cfg.tmpl
+++ b/src/osmo_gsm_tester/templates/osmo-mgw.cfg.tmpl
@@ -15,3 +15,4 @@
  rtcp-omit
  rtp-accept-all 1
  osmux ${mgw.use_osmux}
+ osmux bind-ip ${mgw.ip_address.addr}