setting the compute_driver is mandatory
write the rabbit port only if we have something

the default in the rabbit recipe is nil, so the config would be broken
otherwise
leave the libvirt.conf unmodified for SUSE, the default is better
- implement nova conductor from grizzly
- libvirtd.conf template now suports unix_socket_group defined in
  a attribiutes.
- on suse nova-compute packages is not installing any virtualization technology.
  Implemented support for installing kvm.
- openstack-nova user shuld be member of libvirt group to be able to read
  from libvirt unix_socket. Implemented group resource in libvirt recipie.
Merge pull request #3 from tpaszkowski/grizzly-conductor

-implement nova conductor recipe for grizzly release
Merge pull request #4 from tpaszkowski/grizzly-libvirt

Fixes and improvments for libvirt recipie on suse platform.
Bring back support for xen,lxc and qemu

The packages to install are now attributes.
Merge remote-tracking branch 'saschpe/master-other-virt' into grizzly

Conflicts:
	recipes/libvirt.rb

with fixes