'Tell child cells to send us capabilities.  This is typically
called on startup of the nova-cells service.'

def ask_children_for_capabilities(self, ctxt):

    child_cells = self.state_manager.get_child_cells()
    for child_cell in child_cells:
        message = _TargetedMessage(self, ctxt, 'announce_capabilities', dict(), 'down', child_cell)
        message.process()
