nginx: use jvb IP directly for colibri-ws

web/rootfs/etc/cont-init.d/10-config

@@ -63,11 +63,8 @@ if [[ $DISABLE_HTTPS -ne 1 ]]; then
     fi
 fi
 
-# On environments like Swarm the IP address used by the default gateway need not be
-# the one used for inter-container traffic. Use that one for our fallback ID.
-XMPP_SERVER_IP=$(dig +short ${XMPP_SERVER})
 # export this here to ensure JVB and nginx are in sync about websocket proxy host
-export JVB_WS_SERVER_ID_FALLBACK=$(ip route get ${XMPP_SERVER_IP} | grep -oP '(?<=src ).*' | awk '{ print $1 '})
+JVB_WS_SERVER_ID_FALLBACK=$(dig +short jvb)
 
 # copy config files
 tpl /defaults/nginx.conf > /config/nginx/nginx.conf