Allow setting tls_priority option

Add tls_priority config option to libvirtd.conf config.

libvirt-4.0.0 supports this functionality out of the box.

To fully comply with PROD-27620 priority string should be set in reclass
to the following string:

  SECURE256:-VERS-ALL:+VERS-TLS1.2:-KX-ALL:+ECDHE-RSA:+ECDHE-ECDSA:\
  -CIPHER-ALL:+AES-256-GCM:+AES-256-CBC:-MAC-ALL:+AEAD:+SHA384

Also, fix some inconsistiences found:

* tests/pillar/compute_single.sls - change qemu's group name to 'nova' as
  'cinder' does not exists.

Change-Id: I56a8c3726e1af274e2d2fffce8dca4501745519e
Related-Prod: PROD-27620
(cherry picked from commit 77d9dacf644b1c8a93dcc35d30d90b046b86c9fa)
5 files changed