Icehouse support - Answer file changes

Configuring an extra network on Controller was indeed a mistake.
Analyzing the answers file I got from icehouse and comparing it to the
one I got from havana revealed some changes in Neutron hosts. The L3,
DHCP and METADATA hosts are now all set in CONFIG_NETWORK_HOSTS.
CONFIG_NOVA_COMPUTE_HOSTS was also renamed in icehouse, and is now named
CONFIG_COMPUTE_HOSTS. With these changes, I managed to successfully run
icehouse.