util: fix typo preventing to detect running backend
model: fix VA proxys not being garbage collected

the "optimisation" of recording the getter and setter was not helping well,
because each remote method keeps a pointer to the object, which caused
dependency cycles, preventing garbage collection.

Eventually that was causing a lot of remote connections opened, and never closed,
blocking the access to the backend.
scripts: improvements to odemis-start

handle new state of backend

seems to pretty much work now
model: don't leak containers if the component instantiation failed

when creating a new container for a new component, if the component failed,
the container would just stay there, doing nothing.

That was a little problem before, but now that components can keep failing (every 10s),
we really need to clean up the unused containers.