Add FORCE_CONFIG_DRIVE and make it the default

Adds a new FORCE_CONFIG_DRIVE option to lib/nova which
is by default enabled. Using config drive should speed
things up a bit and is a more likely production default
instead of file injection.

Change-Id: I2388ef0df12a6289b619bfaf30cb952fcc48ef41
Turn off Nova firewall driver when using Neutron

As referenced in the OpenStack documentation, the firewall_driver in
nova.conf should be set to nova.virt.firewall.NoopFirewallDriver, "so
that nova-compute does not perform iptables-based filtering itself".

Without this change, the driver gets set to
nova.virt.libvirt.firewall.IptablesFirewallDriver, which seems to
make networking unusable.

Change-Id: Id9cce0f5f4efe719683aaf3284b128188b61b919
Closes-bug: #1246888
Merge "Turn off Nova firewall driver when using Neutron"
Merge "Add FORCE_CONFIG_DRIVE and make it the default"