Delete DHCP port without DHCP server on a net node

A DHCP-network was deleted from one host using neutron
dhcp-agent-network-remove and then added to another host
using neutron dhcp-agent-network-add command. While the
dhcp-agent-network-remove command was in progress, the
host crashed.  As a result, the removal of the DHCP-network
was partially done. The network was disassociated from
the agent in mysql. However, the agent never made the
release_dhcp_port RPC call to delete the port -- even
after the agent restarted. The end result is that there
are two DHCP ports for the same network. One of these
is found on the host that is no longer hosting the
dhcp-server.

This fix make the DHCP agent invoke the release_dhcp_port
RPC call on a stale network whose dnsmasq process is not
running (not active). Before this change, the RPC call is
made on a stale network only when the dnsmasq process is
running.

Closes-Bug: #1244860
Change-Id: Ie0bafdac698810b5455550c306c6a75ddf91d9bb
Set onlink routes for all subnets on an external network

The addition of the on-link routes gives us some freedom to allocate a
router's IP address from any one of multiple subnets on one external
network.  Different routers can get their IPs from different subnets and
they still have direct on-link connectivity to each other.  For example,
one router with its primary IP from 10.0.0.0/24 and another from
192.168.0.0/24 can communicate directly.  It is important that each
router has on-link routes to *all* of the subnets.

Any router can host floating ips from any of the subnets regardless of
which subnet the primary IP address comes from.

This is an alternative to the "Multiple floating IP pools" section in
the administration guide.  It is a simpler alternative that avoids
having to create multiple external networks.  It is also more flexible
because routers will no longer be restricted to getting floating IPs
from the pool to which they happen to be connected.

DocImpact
Document the procedure for adding subnets to the external network.
Potentially remove the existing procedure for "Multiple floating IP
pools" from the docs.

Change-Id: I2c283f5be0cbb6b5d350cafc1b636c300b796a7b
Closes-Bug: #1312467
Disallow 'timeout' in health_monitor to be negative

It should limit the value of 'timeout' in 'health_monitor', the 'timeout'
shouldn't to be negative.

Change-Id: I26ae1995c9cc362df7c7dda4c53fb8adda298d13
Closes-bug: #1320062
Install SNAT rules for ipv4 only

Change-Id: I37bd770aa0d54a985ac2bec708c571785084e0ec
Closes-Bug: #1309195
NEC plugin: Bump L3RPC callback version to 1.1

update_floatingip_statuses RPC call implemented in Icehouse expects
RPC version 1.1 and RPC version of L3RpcCallback of other plugins
was bumped to 1.1, but the version of L3RpcCallback in NEC plugin
was not bumped to 1.1 yet.

Change-Id: I0073a3de9ea0cd59d43c821f9bdaea89bd125a65
Closes-Bug: #1323769
Merge "Set onlink routes for all subnets on an external network"
Merge "Install SNAT rules for ipv4 only"
Merge "NEC plugin: Bump L3RPC callback version to 1.1"
Merge "Delete DHCP port without DHCP server on a net node"
Merge "Disallow 'timeout' in health_monitor to be negative"