able to run init container with client-go

[ngtuna]

This is a hot fix to have init container running in the case of pubsub function with dependency file. This case was running very well with the old k8s client but when I turned to use client-go this becomes a known bug. Reference issue: kubernetes/client-go#142

[sebgoa]

so that's a bit strange, since in 1.6 we don't need to put annotations for initcontainers to run.

@anguslees can you give your review here, so we can merge and get over this bump

[anguslees]

Wow, what a mess.

It looks like the PodSpec.InitContainers element was added to k8s types.go back in 1.5 (or earlier?), even though the feature wasn't meant to exist in that form at that time. That k8s source file was automatically picked up and copied into the client-go version of types.go. So the client-go 2.0 code has something in the PodSpec type that isn't actually part of the published k8s 1.5 API, contrary to the client-go compatibility statement.

It seems there was some machinery in the k8s code that automatically moved InitContainers values to the appropriate alpha/beta annotations. This machinery doesn't exist or isn't automatically triggered in the client-go version. So kubeless init containers (which were using PodSpec.InitContainers) haven't been working since the move to client-go, when used against <<1.6 k8s. In k8s 1.6, this field suddenly becomes the officially supported way to specify init containers, just to keep things interesting.

Switching to actually using the annotation is the right thing to do, assuming we want to support k8s 1.5, 1.6 and maybe 1.7 (unsure when the beta annotation will be dropped). Yay for using beta API features.

[ngtuna]

Thanks @anguslees for clarifying that. Merging now.