hpcloud-b4's eth0 uses 10.0.3.0/24, which overlaps with the
lxc_net_address default. This commit sets the following in the gate:
lxc_net_address: 10.255.255.1
lxc_net_netmask: 255.255.255.0
lxc_net_dhcp_range: 10.255.255.2,10.255.255.253
At some point we'll need to implement a mechanism to determine valid
lxc_net_address value which will not overlap with an IP already
assigned to the host.
Change-Id: Ib4df050be2d8734c636b6adcc81a53258796b5a8
238c06baa8