Unhardcoded logging level for syslog in Libvirtd (nova-compute)

This patch unhardcodes syslog parameters for libvirtd and qemu in libvirtd.conf
and libvirtd.conf templates accordingly. These parameters might be configured using
the bellow pillar structures:

  nova:
    compute:
      libvirt:
        logging:
          level: 3
          filters: '3:remote 4:event'
          outputs: '3:syslog:libvirtd'
          buffer_size: 64
      qemu:
        logging:
          handler: logd
      virtlog:
        enabled: true
        level: 3
        filters: '3:remote 4:event'
        outputs: '3:syslog:virtlogd'
        max_clients: 1024
        max_size: 2097152
        max_backups: 3

Change-Id: Ic8b3f9ab1e55d9b972ff3baff48312e4dea8a5e5
Related-PROD: PROD-19919
24 files changed