Create proper packaging for downloadable couchbase-operator binary

In the past we've uploaded the -image.tgz file (which is used to communicate between the -build and -docker jobs on Jenkins) as part of the couchbase-operator deliverables, because it was an expedient way to provide a separate download of the couchbase-operator binary outside of the Docker image (required by a particular customer). However this file may have other things in it we don't want to ship, such as source code. The "make dist" step should produce a specific separate tarball that contains exactly what is needed for this deliverable.