Update nova-compute to support baremetal case

Add nova to libvirtd group only when compute.virtualization is kvm.

Unhardcode some nova-compute.config values like:
  * compute_driver
  * ram_allocation_ratio
  * config_drive_format

Add [ironic] section to nova compute config.
Make sure that vnc and image parameters are not mandatory anymore.
Add service level nova.compute.ironic.

Change-Id: I072db910f6f004aad3393d9f6e64b1330de18687
5 files changed