Adds new 'shelve', 'shelveOffload'/'shelve_offload'(V3), and 'unshelve'
actions to the API. Exposes the functionality already provided in the
compute api.
Part of bp shelve-instance
Co-author: Dan Smith <danms@us.ibm.com> (Instance objects)
Change-Id: Idd485b591730c6ac025ee57a1242afdd02191b2f
e53fb7dcdd