hello images are unusable when a cluster is lacking IPv6

[u3813]

As previously pointed out by @PhilipSchmid, the hello images are not starting when a cluster is lacking IPv6 support.

See #53 (comment) for further description.

[PhilipSchmid]

@u3813 Checkout https://github.com/PhilipSchmid/echo-app as a possible replacement for the Nginx hello images.