Add  create and delete to Jumpgate volume API

    1. Support SL portable storage create operation via jumpdate
    2. Support SL portable storage delete operation via jumpdate
    3. Add unittest coverage for jumpgate volume create/delete

Change-Id: I9cd6acb0832279fdfa5080e728ecaef9ac9de638
The second parameter of the .get("display_name", "") will ensure it returns back "" if there is no field of "display_name" found in the body of the post.  JSON encoding doesn't allow passing {"display_name"=None, ... } so this should not be an issue.