Add a new ovs agent extension to support distributed DHCP for
VMs in compute nodes directly. For large scale deployment, this
can be used to reduce the number of neutron agents. Large scale
cloud can benefit from it.
From the perspective of virtual machine, this will reduce the
probability of DHCP request failure. The VMs will get a higher
level availability for DHCP R/R, no single point of failure
permanently. If one host goes down, VMs in other hosts will not
be influnced by it.
For the perspective of network performance, after using this
extension, the DHCP broadcasting packages will be limited
to the host locally.
Partially-Implements: bp/distributed-dhcp-for-ml2-ovs
Closes-Bug: #1900934
Change-Id: Id8a4c501daad7c2185e6d69441182666ef987e61