provider/aws: Update aws_elb policy acctests
provider/aws: Update aws_elb policy acctests

Updates the aws_elb acceptance tests to better handle parallel test runs

 ```
 $ make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSLoadBalancerPolicy_'
 ==> Checking that code complies with gofmt requirements...
 go generate $(go list ./... | grep -v /terraform/vendor/)
 2017/02/09 10:04:58 Generated command/internal_plugin_list.go
 TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSLoadBalancerPolicy_ -timeout 120m
 === RUN   TestAccAWSLoadBalancerPolicy_basic
 --- PASS: TestAccAWSLoadBalancerPolicy_basic (24.50s)
 === RUN   TestAccAWSLoadBalancerPolicy_updateWhileAssigned
 --- PASS: TestAccAWSLoadBalancerPolicy_updateWhileAssigned (42.34s)
 PASS
 ok      github.com/hashicorp/terraform/builtin/providers/aws    66.866s
 ```

nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,Ninir/terraform-provider-aws,ashinohara/terraform-provider-aws,ashinohara/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,ashinohara/terraform-provider-aws,ClementCunin/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,terraform-providers/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws