Remove DHCP lease logic

[OpenStack Infra]

https://review.openstack.org/37580
commit f7e26045ac3792918f7c5fbbd347ff9745beb02d
Author: Aaron Rosen <email address hidden>
Date: Tue Jul 16 16:06:32 2013 -0700

    Remove DHCP lease logic

    Previously neutron was keeping track of dhcp lease time in order
    to ensure it didn't hand out an ip address that was already leased.
    This patch removes that logic and instead leverages the dhcp_release
    utility. This allows us to reuse ip addresses immediately after a port
    is deleted. This patch also bumps the lease time to 24 hours instead
    of 2 minutes with reduces the amount of dhcp traffic.

    DocImpact

    There is a DocImpact for this bug related to the upgrade path. One should
    first upgrade their dhcp-agents. Then wait till the dhcp_lease time has
    expired. Lastly, update neutron-server in order to avoid the case where
    an instance is deleted and the dnsmasq process has not released the lease
    and neturon allocates that ip to a new port.

    Fixes bug: 1202392
    Implements blueprint: remove-dhcp-lease

    Change-Id: Ifcb4f093c92904ceb896438987d53e692eb7fb26

[Jon Proulx (jproulx)]

Since the doc impact is about upgrade order this should go in the release notes, not the network admin guide, yes?

if so then I did it:
https://wiki.openstack.org/wiki/ReleaseNotes/Havana#Upgrade_Notes_6