Add a delay in the verify script for the externalname test.

This test also intermittently gets 503 responses immediately after
the config is loaded.

examples/externalname/verify.sh

@@ -15,4 +15,7 @@ kubectl port-forward svc/varnish-ingress ${LOCALPORT}:80 >/dev/null &
 trap 'kill $(jobs -p)' EXIT
 wait_for_port ${LOCALPORT}
 
+# XXX intermittent 503 responses immediately after the config is valid.
+sleep 10
+
 varnishtest ${TESTOPTS} -Dlocalport=${LOCALPORT} ../hello/cafe.vtc