Instead of insisting on perfect equality of score
allow for numerical inaccuracies and consider everything
all differences in the cluster score smaller than 1e-12
negligible. Given that, by default, a cluster with a
score of less than 1e-9 is considered perfectly balanced,
this relaxation is on the save side.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>