This test overrides the AWS_DEFAULT_REGION parameter as the security
groups are created in us-east-1 (due to classic VPC requirements)
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSDBSecurityGroup_importBasic'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
TF_ACC=1 go test ./builtin/providers/aws -v
-run=TestAccAWSDBSecurityGroup_importBasic -timeout 120m
=== RUN TestAccAWSDBSecurityGroup_importBasic
--- PASS: TestAccAWSDBSecurityGroup_importBasic (49.46s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 49.487s
```
db_security_group is only intended to be used in EC2-Classic Platform.
For DB instances in a VPC, we associate VPC security groups instead,
when declaring the db_instance resource.
The Terraform configuration syntax defines what arrays are.
Use the word array consistently throughout the documentation
instead of list.
The corresponding JSON datatype is called array as well, and
since the Terraform configuration syntax is interoperable with
JSON it makes sense to use the term array to describe them.
