LA rebalancer tries to amend non-fixable policy violations in case of RF=2 and three and more locations

In case of RF=2 and more than two locations, the logic of the LA rebalancer suggests a fix for the distribution of replicas, and the rebalancer loops indefinitely trying to implement the suggested replica movements.

However, RF=2 is a special case: any replica distribution of a tablet with RF=2 is a violations of the placement policy constraints and it's impossible to fix that, regardless of number of locations in the cluster.