upgrade levels

[Rafal]

Documentation regarding upgrade_levels in operations guide may be misleading.

https://docs.openstack.org/operations-guide/ops-upgrades.html

It suggests that upgrade level should be locked to version X+1 (new one?) where in fact it should be locked to current (old) one.

It is:

[upgrade_levels]
compute=X+1
conductor=X+1
scheduler=X+1

It should be:

[upgrade_levels]
compute=X
conductor=X
scheduler=X

This is also correctly described in nova's documentation of this configuration option:

https://github.com/openstack/nova/blob/master/nova/conf/upgrade_levels.py#L35