Ensure network_id is in the vlan mappings

Change-Id: Id5f09e9dc55212c7a4350335d5fcb792f0388ba3
Create a new attribute for subnets, to store v6 dhcp options

Backwards compatability is preserved by setting the mode to
'static' when the attribute is not defined.

Implements bp dnsmasq-mode-keyword

Change-Id: I5b2313fff5dca1c16ff939fdc4397d7f95ba3ba5
Calculate stateless IPv6 address

In order to support stateless IPv6, neutron should
calculate IPv6 address base on IPv6 prefix and MAC
address via EUI-64 specification, and assign this
address to target instance. Also assume the instance
will be assigned with the same IPv6 address

Implements bp dnsmasq-mode-keyword

Change-Id: I68ccbc42388ec760d6fead242e080822ca753913
Change subnet_mode migration script for comcast branch

Change-Id: Ib82b750701ccb22838f46158e618cf52b19ac895
Fix missing import

Change-Id: I69bd8d06e271b9e0f34bee8b4efb2e3f77302143
Ensure that that all fixed ips for a port belong to a subnet using DHCP

In certain configurations, Neutron calculates SLAAC addresses for IPv6
subnets and adds them to the fixed_ips field of a port. Since those
subnets are not being managed by DHCP, do not add those fixed_ip entries
to the host file.

Implements blueprint ipv6-provider-nets-slaac

Change-Id: I77dd55063296990c9df385f331f5de5d42402786
Fix unit tests

Change-Id: I825b6d93bbcc1cfeee53b70392acb9382d323135
PEP8

Change-Id: I9ee6116efdb111af5b4fc785e07c60d4e5b2cc9a