Defer calls to tripleoclient.object_store
Defer calls to tripleoclient.object_store

With a recent osc-lib[1] change it is no longer possible to make
auth-requiring calls in the command __init__.

This change defers calls to tripleoclient.object_store so that it is
made when auth is properly setup.

[1] I72ae6154268bdf26be6054c0fef6a4c67c71119c
Closes-Bug: #1687032

Change-Id: If640da00d9b8d49ff935209e3b31dcf0f327ad63

openstack/python-tripleoclient