Updated openstack/openstack
Project: openstack/neutron  b52e6c3afb4fedc77c73a6142ca4cbf6e5ef953f

Raise proper exception in case duplicate ipv6 address is allocated

In case neutron tries to generate ipv6 address for slaac subnet,
it doesn't check that generated ip is unique and throws DB exception
that results in 500 HTTP error.

The fix throws proper IpAddressInUse exception.

Closes-Bug: #1358731
Change-Id: I66aed81b8d31d1eff6c87a77c4c4a813179ba458