Only setup nova-dhcpbridge if using nova-network

Closes-Bug: #1705324

Change-Id: I3abc84483bbd256e0bbbfe64d570903080f2a2b7

lib/nova

@@ -541,6 +541,7 @@ function create_nova_conf {
     # Setup logging for nova-dhcpbridge command line
     sudo cp "$NOVA_CONF" "$NOVA_CONF_DIR/nova-dhcpbridge.conf"
 
+    if is_service_enabled n-net; then
         local service="n-dhcp"
         local logfile="${service}.log.${CURRENT_LOG_TIME}"
         local real_logfile="${LOGDIR}/${logfile}"
@@ -554,6 +555,7 @@ function create_nova_conf {
         fi
 
         iniset $NOVA_CONF DEFAULT dhcpbridge_flagfile "$NOVA_CONF_DIR/nova-dhcpbridge.conf"
+    fi
 
     if [ "$NOVA_USE_SERVICE_TOKEN" == "True" ]; then
         init_nova_service_user_conf