tests/resource/aws_elb: Switch test configurations to data sources to be region agnostic
tests/resource/aws_elb: Switch test configurations to data sources to be region agnostic

While this gets the acceptance testing working in GovCloud (US), it does now also highlight a bug similar to https://github.com/terraform-providers/terraform-provider-aws/issues/9304

Output from acceptance testing in AWS Commerical:

```
--- PASS: TestAccAWSELB_disappears (68.68s)
--- PASS: TestAccAWSELB_ConnectionDraining (76.74s)
--- PASS: TestAccAWSELB_namePrefix (93.59s)
--- PASS: TestAccAWSELB_AccessLogs_enabled (103.17s)
--- PASS: TestAccAWSELB_generatedName (106.01s)
--- PASS: TestAccAWSELB_fullCharacterRange (106.48s)
--- PASS: TestAccAWSELB_importBasic (112.57s)
--- PASS: TestAccAWSELB_generatesNameForZeroValue (122.21s)
--- PASS: TestAccAWSELB_basic (130.19s)
--- PASS: TestAccAWSELB_HealthCheck (133.04s)
--- PASS: TestAccAWSELB_Listener_SSLCertificateID_IAMServerCertificate (136.34s)
--- PASS: TestAccAWSELB_SecurityGroups (142.99s)
--- FAIL: TestAccAWSELB_listener (148.51s)
    testing.go:568: Step 4 error: errors during plan:

        Error: insufficient items for attribute "listener"; must have at least 1

    testing.go:629: Error destroying resource! WARNING: Dangling resources
        may exist. The full state and error is shown below.

        Error: errors during refresh: insufficient items for attribute "listener"; must have at least 1

        State: <nil>
--- PASS: TestAccAWSELB_AccessLogs_disabled (154.64s)
--- PASS: TestAccAWSELB_tags (155.92s)
--- PASS: TestAccAWSELB_Timeout (168.71s)
--- PASS: TestAccAWSELB_availabilityZones (210.40s)
--- PASS: TestAccAWSELB_swap_subnets (228.13s)
--- PASS: TestAccAWSELB_InstanceAttaching (527.69s)
```

Output from acceptance testing in AWS GovCloud (US):

```
--- PASS: TestAccAWSELB_availabilityZones (88.33s)
--- PASS: TestAccAWSELB_tags (113.93s)
--- PASS: TestAccAWSELB_Timeout (115.69s)
--- PASS: TestAccAWSELB_importBasic (123.79s)
--- PASS: TestAccAWSELB_swap_subnets (124.01s)
--- PASS: TestAccAWSELB_Listener_SSLCertificateID_IAMServerCertificate (147.94s)
--- PASS: TestAccAWSELB_HealthCheck (149.88s)
--- PASS: TestAccAWSELB_SecurityGroups (154.84s)
--- PASS: TestAccAWSELB_disappears (200.13s)
--- PASS: TestAccAWSELB_namePrefix (200.70s)
--- PASS: TestAccAWSELB_fullCharacterRange (213.47s)
--- PASS: TestAccAWSELB_generatesNameForZeroValue (214.22s)
--- PASS: TestAccAWSELB_generatedName (229.05s)
--- PASS: TestAccAWSELB_ConnectionDraining (230.66s)
--- PASS: TestAccAWSELB_basic (240.03s)
--- FAIL: TestAccAWSELB_listener (268.22s)
    testing.go:568: Step 4 error: errors during plan:

        Error: insufficient items for attribute "listener"; must have at least 1

    testing.go:629: Error destroying resource! WARNING: Dangling resources
        may exist. The full state and error is shown below.

        Error: errors during refresh: insufficient items for attribute "listener"; must have at least 1

        State: <nil>
--- PASS: TestAccAWSELB_AccessLogs_enabled (275.48s)
--- PASS: TestAccAWSELB_AccessLogs_disabled (298.22s)
--- PASS: TestAccAWSELB_InstanceAttaching (306.86s)
```

terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws