pkg-export-k8s: Make use of new export-docker API
pkg-export-k8s: Make use of new export-docker API

Use the new API in export-docker crate to add the mandatory package
identifier argument to the CLI.

Signed-off-by: Zeeshan Ali <f7a8e49325fe4a238df42df4f7e30abcfdad87c6@kinvolk.io>

georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,nathenharvey/habitat,habitat-sh/habitat,georgemarshall/habitat,rsertelon/habitat,nathenharvey/habitat,habitat-sh/habitat,georgemarshall/habitat,nathenharvey/habitat,rsertelon/habitat,georgemarshall/habitat,rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,georgemarshall/habitat,nathenharvey/habitat,habitat-sh/habitat,rsertelon/habitat,georgemarshall/habitat,georgemarshall/habitat,nathenharvey/habitat,georgemarshall/habitat,nathenharvey/habitat,habitat-sh/habitat