This is to avoid IP clashes between instances and the host. In an AIO
scenairo the host br-vlan bridge has 172.29.248.100 which is within the
cidr allocated to instances. This patch specifies an allocation pool:
172.29.249.110-172.29.249.200 which doesn't conflict with any
statically allocated IPs in the AIO config.
Change-Id: If330c94025dd21229a34aa03d1ca3a75b3a3ea8c
Informal-Dependency: Ia58a6447ef28ba5d4ae2a2ac769ad0cc287f448d
Partial-Bug: #1564491
d87fdf252c