provider/aws: Make iam_user_policy_attachment_test work as expected: (#9733)
provider/aws: Make iam_user_policy_attachment_test work as expected: (#9733)

Was failing due to using IAM user `test-name` as it was being used in
more than 1 place - this has been replaced by a random user and random
policy names now

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSUserPolicyAttachment_basic'                                                                               2 ↵ ✹
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2016/10/31 08:39:08 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSUserPolicyAttachment_basic -timeout 120m
=== RUN   TestAccAWSUserPolicyAttachment_basic
--- PASS: TestAccAWSUserPolicyAttachment_basic (32.04s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	32.053s
```
Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,ClementCunin/terraform-provider-aws,kjmkznr/terraform-provider-aws,ashinohara/terraform-provider-aws,kjmkznr/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws,terraform-providers/terraform-provider-aws,ashinohara/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,nbaztec/terraform-provider-aws,ClementCunin/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,ClementCunin/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws