Updates `aws_caller_identity` data source to actually include the correct attributes from the `GetCallerIdentity` API function.
```
$ make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSCallerIdentity_basic'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/27 09:26:13 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSCallerIdentity_basic -timeout 120m
=== RUN TestAccAWSCallerIdentity_basic
--- PASS: TestAccAWSCallerIdentity_basic (12.74s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 12.767s
```
This data source provides access during configuration to the ID of the
AWS account for the connection to AWS. It is primarily useful for
interpolating into policy documents, for example when creating the
policy for an ELB or ALB access log bucket.
This will need revisiting and further testing once the work for
AssumeRole is integrated.
Radek Simko