lib: graph: disallow recursive consuming

Do not allow a user component to consume or run its parent graph if the
graph is in one of the following states (operations):

* Consuming (running)
* Connection ports
* Adding (creating) a component

test_graph.py tests this feature through the Python bindings.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>