[Pacemaker] symmetric anti-collocation

[Alan Jones]

>> I have tried larger values.  If you know of a value that *should*
>> work, please share it.
>
> INFINITY

My understanding is that a colocation score of minus infinity will
prevent the resources from running on the same node, which in my
configuration would result in a loss of availability.  The goal is a
value that will overrule the node location preferences of one, allow
for both resources to run on the same node, and provide for
anti-colocation to evict either resource based on the constraints of
the other.  I can't claim to understand your code, but I've done
sufficient experiments to understand the code's behavior in 1.0.9.1.
There is simply no combination of colocation rules and values that
will work in both directions.  I can get the placement of Y to evict X
-- or -- X to evict Y; but not both.
Alan