Call child.make_query_plan in TokenAwarePolicy.make_query_plan only once

[dkropachev]

In some scenarios TokenAwarePolicy.make_query_plan can call child.make_query_plan three times.
Let's make sure it is called only once.

python-driver/cassandra/policies.py

Lines 506 to 539 in 2739b29

	def make_query_plan(self, working_keyspace=None, query=None):
	keyspace = query.keyspace if query and query.keyspace else working_keyspace
	child = self._child_policy
	if query is None or query.routing_key is None or keyspace is None:
	for host in child.make_query_plan(keyspace, query):
	yield host
	return
	replicas = []
	if self._tablets_routing_v1:
	tablet = self._cluster_metadata._tablets.get_tablet_for_key(
	keyspace, query.table, self._cluster_metadata.token_map.token_class.from_key(query.routing_key))
	if tablet is not None:
	replicas_mapped = set(map(lambda r: r[0], tablet.replicas))
	child_plan = child.make_query_plan(keyspace, query)
	replicas = [host for host in child_plan if host.host_id in replicas_mapped]
	if not replicas:
	replicas = self._cluster_metadata.get_replicas(keyspace, query.routing_key)
	if self.shuffle_replicas:
	shuffle(replicas)
	for replica in replicas:
	if replica.is_up and child.distance(replica) in [HostDistance.LOCAL, HostDistance.LOCAL_RACK]:
	yield replica
	for host in child.make_query_plan(keyspace, query):
	# skip if we've already listed this host
	if host not in replicas or child.distance(host) == HostDistance.REMOTE:
	yield host

[mykaul]

Covered by #651