pkg-export-k8s: Use versioned tag when '-d' is passed
pkg-export-k8s: Use versioned tag when '-d' is passed

Currently when docker image generation is disabled, the exporter uses
`latest` tag for docker image even if version information is available.
This patch fixes this issue.

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

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