3.x: Fix LWT routing

[dkropachev]

Currently LWT routing does not involve LoadBlancingPolicy at all

java-driver/driver-core/src/main/java/com/datastax/driver/core/RequestHandler.java

Lines 146 to 154 in dbfe82a

	} else if (statement.isLWT()) {
	this.queryPlan =
	new QueryPlan(
	getReplicas(
	manager.poolsState.keyspace,
	statement,
	manager
	.loadBalancingPolicy()
	.newQueryPlan(manager.poolsState.keyspace, statement)));

And returns vnode/tablet replicas as they are.
As result if user configured cluster with TokenAwarePolicy+DCAwareRoundRobinPolicy/RackAwareRoundRobinPolicy as LoadBalancingPolicy they expect to see queries routed to a particular DC, but driver voids rack/dc awarness and route traffic to first replica first, which could be from another Dc/Rack.

[dkropachev]

Was partially fixed here - #385, rest part of the issue to be addressed in #752