refactor ovirt_store_config to native python

This split ovirt_store_config into a new ovirt_store_config_atomic to ensure that stored files are
done atomically to avoid inconsistent configuration failures

rhbz#871212

Signed-off-by: Joey Boggs <jboggs@redhat.com>
Change-Id: Ic37903fb70f006fda133533b93515a654b32de8a