provider/aws: Fix matching regexp in invalid role config test
provider/aws: Fix matching regexp in invalid role config test

```
$ make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSRole_badJSON'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/02/16 10:08:07 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSRole_badJSON -timeout 120m
=== RUN   TestAccAWSRole_badJSON
--- PASS: TestAccAWSRole_badJSON (0.00s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/aws    0.011s
```

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