Implements securitygroup extension for nuage plugin

In Nuage VSP, the scope of vport-tag(Neutron securitygroup equivalent) is either
per router or per subnet whereas securitygroup scope in Neutron is per tenant.
Because of this, the mapping between neutron and VSP resource always happens at
the port create or update time, such that port's router/subnet is known and
thus sg attachment point in VSP is known.
On port-update --security-group sg1, if this is the first port getting attached
to that security-group, corresponding vport-tag(for sg) and rules( for sg rules)
are created on VSP. Subsequent port-update for the same sg1 will just update the
port to vport-tag binding. When security-group and security-group-rules are
deleted on neutron, corresponding vport-tag and rules are deleted on the VSP.

Implements: blueprint securitygroup-ext-for-nuage-plugin

Change-Id: If6f7f16ad727ae9394008fb81b56c785c2404c8f
Support Stateful and Stateless DHCPv6 by dnsmasq

* This patch adds support for subnets created with 'ipv6_address_mode'
  set to 'dhcpv6-stateful' or 'dhcpv6-stateless' by dnsmasq.
* If no dnsmasq process for subnet's network is launched, Neutron
  will launch new dnsmasq process on subnet's dhcp port in 'qdhcp-'
  namespace. If previous dnsmasq process is already launched,
  restart dnsmasq with new configuration.
* Neutron will update dnsmasq process and restart it when subnet
  gets updated.
* This patch enforces the version check of dnsmasq. dhcp-agent will
  fail to start if version of dnsmasq<2.63.

DocImpact
UpgradeImpact
Blueprint dnsmasq-ipv6-dhcpv6-stateful
Blueprint dnsmasq-ipv6-dhcpv6-stateless

Change-Id: I30e9950bbc5a89f01ccb9c561471f155a9fd1d11
Merge "Implements securitygroup extension for nuage plugin"
Merge "Support Stateful and Stateless DHCPv6 by dnsmasq"