Allow listing fixed_ips for a given compute host.

nova.db.fixed_ip_get_all_by_instance_host was removed in commit
bb867ce3948ddc23cf928ca3dda100a1a977896a, but was still used in
nova-manage. This patch works around the removal of the foreign
key that led to this method being removed.

Resolves bug 1163660.

Change-Id: Ieccd37c752e245558827615c098604d11ad3d945
Merge "Allow listing fixed_ips for a given compute host." into stable/grizzly