Matthew,
I think it's not the same situation as with Keystone user and its password, or probably I misunderstood you.
The problem here is that when you rename the default network after deployment (net04, for example) and then re-run puppet modules (during scaling and so on), neutron_network provider checks that a network with the default name (net04) exists and tries to create it. As the network was renamed, in fact it doesn't exist anymore for neutron_network provider, so it tries to create it again.
Matthew,
I think it's not the same situation as with Keystone user and its password, or probably I misunderstood you.
The problem here is that when you rename the default network after deployment (net04, for example) and then re-run puppet modules (during scaling and so on), neutron_network provider checks that a network with the default name (net04) exists and tries to create it. As the network was renamed, in fact it doesn't exist anymore for neutron_network provider, so it tries to create it again.