Comment 2 for bug 1063689

What value is set to network_manager in your nova.conf?
I guess network_manager in your nova.conf is "quantum.manager" or something.

network_manager in nova.conf has no meaning In Folsom quantum, but this configuration parameter must point a valid python module like "nova.network.manager.VlanManager".

Since You seems to have create your config file from the Essex version,
commenting out or removing "network_manager" line from nova.conf may help you.

It would be better we should add a note about network_manager in nova.conf in the Folsom version of quantum admin guide.