Cosmetic changes
createLoadBalancer: Fix Subnets parameter and add a test case
Add a test case for attachLoadBalancerToSubnets and detachLoadBalancersFromSubnets
Add a test case for applySecurityGroupsToLoadBalancer
Add a test case for {create,delete}LoadBalancerListeners
Add a test case for registerInstancesWithLoadBalancer and deregisterInstancesFromLoadBalancer