The k8 example cayley-mongo is broken

I spent the evening fiddling with it. For one thing, the image tag it refers to, `v0.7.0-alpha`, no longer exists. I switched to master but then the initialization container never finished setting up. I tried removing that since the normal cayley container has initialization arguments, and this caused the services to all start without any errors. Still, I was never able to get an http response from the container.

The other k8 example with BoltDB backend worked fine for me, but this one is much older. I assume it just needs to be rewritten by someone who knows what they're doing.

Start by comparing the broken k8 cayley-mongo example with the working BoltDB example, then inspect the referenced image tag and initialization container behavior. Done means the example uses an available image, completes initialization, starts its services without errors, and returns an HTTP response.

Written by the indexing model from the issue text.