Port nova.conf to Grizzly

No need to conditionalize rabbit_settings, the recipe won't catch that
either. Config values that we set the same as upstream have been removed.
'logdir' is the deprecated name for 'log_dir'. Explicitly set
glance_host / glance_port. The option
'dhcpbridge_flagfile=/etc/nova/nova.conf' could have never worked, since
dnsmask config files look entirely differnt
(http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq.conf.example), thus
use the upstream default.

We only set public_interface when using nova-network and if the node has
a public IP, otherwise upstream default. Since this is Eth0, I assume we
rather want None. Similarly, I guess we want api_rate_limit=True
(default).

Dropped outdated config options:

 additional_compute_capabilities=pv,hvm (xen)
 daemonize=True
 root_helper=sudo nova-rootwrap
 enable_zone_routing=true
 allow_admin_api=true
 use_deprecated_auth=false
 connection_type=libirt

SUSE Notes:

A "auto_assign_floating_ip" config value exists for nova-network, don't
know if quantum implements that in Grizzly.
Port nova.conf to Grizzly / rework vnc settings.

As far as I can see it makes no sense to conditionalize novnc / xvpvnc proxy
config values. Defaults are applied anyway and whether these values are
used or not depends on which vnc binary / service is used.
Port nova.conf to Grizzly / Remaining network parts

Dropped outdated config options:

  flat_network_dhcp_start
  image_service (it's always Glance)
  floating_range (but the project recipe still uses it)
  libvirt_vif_type
Properly set metadata_proxy_shared_secret in nova.conf
Incorporate changes from recent merges