Move db migration of ml2 security groups to havana

ml2 plugin is a havana feature. Currently securitygroups table are
created in chain of migration after havana release. It causes db
migration failure when migrating from havana to current head because
securitygroups table is attempted to be created although it was already
created by create_all().

Closes-bug: #1271231
Change-Id: If450bd95de7a5fdfdb2219cfbf7eb0c1323044bb
Make sure dnsmasq can distinguish IPv6 address from MAC address

Currrently, due to in dnsmasq host file, the IPv6 address does
not be wrapped with '[]', dnsmasq cannot distinguish IPv6 address
from MAC address, it will cause the deployed instances cannot get
IPv6 address via dnsmasq dhcp service.

Change-Id: I023e44667a238664d11f2ac2cc484432cd301bcc
Closes-Bug: #1281916
Avoid using "raise" to reraise with modified exception

The code changes the exception and reraises it.
This commit changes the code to use the same way as
excutils.save_and_reraise_exception does to ensure
the exception context.

This is the last patch of reraise clean up series.

Closes-Bug: #1279813
Change-Id: I8787dcbdc8321f75964de26e97cae395707aafc2
BigSwitch: Add address pair support to plugin

Adds support for the address pair extension to
the BigSwitch/restproxy plugin.

Implements: blueprint bsn-address-pairs
Change-Id: If03e8752155bcb8b21f5a427c54640c5b63f77f3
Merge "Avoid using "raise" to reraise with modified exception"
Merge "Move db migration of ml2 security groups to havana"
Merge "Make sure dnsmasq can distinguish IPv6 address from MAC address"