provider/aws: Allow `aws_alb` to have the name auto-generated
provider/aws: Allow `aws_alb` to have the name auto-generated

In order to satisify scenarios where a lifecycle is block is used, we
would need the AWS ALB name field to be autogenerated. WE follow the
same work as AWS ELB, we prefix it with `tl-lb-`

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSALB_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/09/08 12:43:40 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSALB_ -timeout
120m
=== RUN   TestAccAWSALB_basic
--- PASS: TestAccAWSALB_basic (79.81s)
=== RUN   TestAccAWSALB_generatedName
--- PASS: TestAccAWSALB_generatedName (93.81s)
=== RUN   TestAccAWSALB_namePrefix
--- PASS: TestAccAWSALB_namePrefix (73.48s)
=== RUN   TestAccAWSALB_tags
--- PASS: TestAccAWSALB_tags (181.32s)
=== RUN   TestAccAWSALB_noSecurityGroup
--- PASS: TestAccAWSALB_noSecurityGroup (66.03s)
=== RUN   TestAccAWSALB_accesslogs
--- PASS: TestAccAWSALB_accesslogs (130.82s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/aws    625.285s
```

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