Fix nova-manage backend_add with sr_uuid
Fix nova-manage backend_add with sr_uuid

Fixes bug 950964

Remove FIXME in db.sm_backend_conf_get_by_sr
Add first() to sm_backend_conf_get_by_sr query
Change db/api.py:sm_backend_conf_get_by_sr to call correct impl method
Have nova-manage generate an actuall sr_uuid instead of always 'None'
Actually update backend values when specifying uuid

Change-Id: I620da4563d8c936b5a072c4683ae145280104fc2

n0ano/ganttclient