[ClusterLabs] Important note for anyone using guest nodes and upgrading to 1.1.18

[Ken Gaillot]

This will also be of interest to distribution packagers ...

There is a bug fix in 1.1.18 that may expose user cases that were
relying on the old (less desirable) behavior.

In 1.1.18, guest nodes (e.g. VirtualDomain resources with a remote-node 
parameter) will now be probed for resource status just like any other
node.

If someone had a use case where they used a -INFINITY location
constraint to keep a resource off a guest node where it can't run (e.g.
due to the software not being installed), they *should* have also used
the resource-discovery=never constraint option to keep Pacemaker from
probing the resource there. However, it wasn't necessary, since guest
probes weren't implemented. Now that they are, they will start getting
probe failures if they don't have resource-discovery=never.

Probes are important for two particular cases: detecting when a
resource is already running outside cluster control, and re-detecting
resource status after a clean-up. So, reverting the behavior would not
be a good idea; the solution really is to use resource-discovery=never
when appropriate.
-- 
Ken Gaillot <kgaillot at redhat.com>