Fixes and improvments for libvirt recipie on suse platform.


    - libvirtd.conf template now suports unix_socket_group defined in
      a attribiutes (with specific configuration for suse).
    - 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.