HBASE-12664 TestDefaultLoadBalancer.testBalanceCluster fails in CachedDNSToSwitchMapping

Conflicts:
	hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestDefaultLoadBalancer.java
	hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancer.java