* Remove unused MIDONET specific settings from nova.conf
* Remove unused MIDONET specific settings from dhcp_agent.ini
* Move the interface_driver settings to the proper setting
function so that it can be used by lbaas_agent.ini as well.
Change-Id: Id686ff5f55db00bce42b8a2bd56e7655c73211fb
Closes-Bug: #1245401