[Pacemaker] Looking for correct constraints

[Dominik Klein]

> Maybe set a cluster-wide attribute, which, when set, does not allow res2
> to run. Ie rule with score -infinity.
> 
> res1 could remove this attribute while starting and set this attribute
> when stopping.

This does not make any sense. Sorry, let me try again.

res1 start = set attribute
res1 stop = delete attribute

rule for res2 with -inf score if attribute is set.

Hope it makes sense now.