Cloned from launchpad blueprint https://blueprints.launchpad.net/neutron/+spec/lbaas-common-agent-driver.

Description:

Current haproxy-on-host driver implementation which is using agents is quite specific:
 - with haproxy it is easier to deploy the whole loadbalancer config from scratch every time
   then to create/update/delete separate components
 - namespace driver needs virtual interface driver on init, 
   other drivers may have their own specific parameters

So it is useful to unify reference agent implementation to:
 - make it suite any driver which wants to use async mechanism
 - have single lbaas agent type and hense single agent scheduling mechanism

All we need is a small revision of agent API and agent mechanism of loading device driver(s)

Specification URL (additional information):

https://wiki.openstack.org/wiki/Neutron/LBaaS/CommonAgentDriver