Fix condition on DiscreteReal Atomic for non-Range data type

[fsaad]

spn = (X << poisson(mu=5))
w = spn.condition(X << {1,2,3, 10})

The conditional distribution needs to be a mixture of atoms, instead of assuming full support on the bounds.

[fsaad]

Specifically the assumption of full support between

        self.xl = float(support.inf)
        self.xu = float(support.sup)