hack/versions: extract most from vendor.conf

This sets `$what_VERSION` and `$what_REPO` for runc, cni, containerd and
kubernetes based on vendor.conf, removing the need to duplicate things in
hack/versions.

With this `update_hack_versions` becomes redundant so remove it and both calls.

Since CONTAINERD_REPO is now unconditionally set we can also simplify the
fetching of vendor.conf in update-vendor.sh a bit, so do so. Further since
`*_REPO` are now unconditionally set we can support alternative clone paths for
all of these repos by adjusting checkout_repo to make the 3rd argument
non-optional and always passing it. Since `CRITOOL_VERSION` is not coming from
`vendor.conf` (since it is not used from Go code) we manually set
`CRITOOL_REPO` for consistency.

The final wrinkle is that `k8s.io/kubernetes` is has a Go specific redirect in
the form of HTML meta headers returned from https://k8s.io/kubernetes/?go-get=1
which point to the real repo to clone. Parsing that in shell is tricky so just
hardcode that.

Fixes #540.

Signed-off-by: Ian Campbell <ijc@docker.com>

hack/versions

@@ -1,6 +1,14 @@
-RUNC_VERSION=9f9c96235cc97674e935002fc3d78361b696a69e
-CNI_VERSION=v0.6.0
-CONTAINERD_VERSION=f12ba2407e328c98f8be5eacbb9c510b073dd4c0
-CONTAINERD_REPO=
+from-vendor RUNC       github.com/opencontainers/runc
+from-vendor CNI        github.com/containernetworking/plugins
+from-vendor CONTAINERD github.com/containerd/containerd
+from-vendor KUBERNETES k8s.io/kubernetes
+
+# k8s.io is actually a redirect, but we do not handle the go-import
+# metadata which `go get` and `vndr` etc do. Handle it manually here.
+if [ x"$KUBERNETES_REPO" = "xk8s.io" ] ; then
+    KUBERNETES_REPO="https://github.com/kubernetes/kubernetes"
+fi
+
+# Not from vendor.conf.
 CRITOOL_VERSION=240a840375cdabb5860c75c99e8b0d0a776006b4
-KUBERNETES_VERSION=0caa20c65f147e15f5545862510eb7e81c42b0a3
+CRITOOL_REPO=github.com/kubernetes-incubator/cri-tools