* stable-2.9
  Version bump for 2.9.0 rc2
  Update NEWS for 2.9.0 rc2
  Downgrade 'vif_script'
  Downgrade 'xen_cmd'
  Add test cluster config for version 2.9
  Remove superfluous import of 'errors'
  Start NEWS entry for 2.9.0 rc2
  Fix lint errors
  Fix upgrade and downgrade regarding disk.dev_type
  Rename LDS_DRBD to DTS_DRBD

* stable-2.8
  Fix typo in walkthrough documentation
  Don't attemp ipv6 ssh in case of ipv4 cluster
  Fix outdated documentation for users-setup

Conflicts:
	NEWS: trivial
	configure.ac: ignore suffix bump on stable-2.9
	lib/constants.py: manually replay 66a37e on master
	lib/objects.py: manually apply the LDS -> DTS change on master
	test/data/cluster_config_2.9.json: take version of stable-2.9
	tools/cfgupgrade: union of all Upgrade tasks, remove all downgrade paths from stable-2.9

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Jose A. Lopes <jabolopes@google.com>