OS::Neutron::Net should determine dhcp_agent to run dnsmasq.

[Ryo Miki]

Some resources can determine "HOST" by "availability_zone:host" property in HOT.
e.g.(OS::Nova::Server, OS::Cinder::Volume)

To determine a dhcp_agent to run dnsmasq for the network,
Neutron supports dhcp-agent-xxx CLI.
But this function is unavailable in OS::Neutron::Net.

This parameter may not be needed by users,
but must be needed by administrators.

[Example]
a) When administrators would like to control agent-server
   to run dnsmasq before the network resource has been created.
b) When agent-server is scheduled in maintenance,
   resources on the server must be moved.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/59626

[Ryo Miki (miki-ryo-e)]

Above is my first patch in OpenStack community :)
Any comments and suggestions are welcomed.

I deleted "my idea" in bug description since I think this implementation should be new resource.
(I named the resourse OS::Neutron::NetDhcpAgent.)

because:
- it is more simple implementation than adding property in OS::Neutron::Net
- relation between network and dhcp-agent isn't 1:1
- i think multiple kind of APIs in handle_create (and other functions) are not welcome

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/59626
Committed: http://github.com/openstack/heat/commit/5b61c4ca2d9adabb482442e737b0e7872226bce3
Submitter: Jenkins
Branch: master

commit 5b61c4ca2d9adabb482442e737b0e7872226bce3
Author: Ryo Miki <email address hidden>
Date: Wed Nov 27 02:12:12 2013 +0900

    Add OS::Neutron::NetDHCPAgent for neutron/net.py

    This resource supports part of "agent management and scheduler
    extensions" in Neutron. It associates network with dhcp-agent.

    I think, it may be needed by administrators who want to decide agents to
    work. (e.g. to use HA functionality)

    Closes-bug: #1245366
    Change-Id: I3dc663c4c51824bd3e69c74ff1d9b50a8ce598c9