[docker] functions to access the registry api v2

docker_registry_funcs.sh

#!/bin/bash

HOST=my_registry

getJsonVal () { 
    python -c "import json,sys;sys.stdout.write(json.dumps(json.load(sys.stdin)$1))"; 
}

get_tags () {
    i_name=$1
    curl -s ${HOST}:5000/v2/${i_name}/tags/list | getJsonVal "['tags']"
}

remove_image() {
    i_name=$1
    i_ver=$2
    digest=$(curl -i -s -H "application/vnd.docker.distribution.manifest.v2+json" \
        -X GET  http://${HOST}:5000/v2/${i_name}/manifests/${i_ver} \
        | grep Etag | cut -d '"' -f2)
    echo Removing $digest
    curl -v -X DELETE http://${HOST}:5000/v2/${i_name}/manifests/${digest}
}