* provider/aws: Deprecate roles in favour of role in iam_instance_profile
You can only specify a single role to an IAM Instance Profile. So having
a slice of roles in the provider makes no sense. Therefore, we are going
to deprecate this infavour of `role`
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSIAMInstanceProfile_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/28 21:24:20 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSIAMInstanceProfile_ -timeout 120m
=== RUN TestAccAWSIAMInstanceProfile_importBasic
--- PASS: TestAccAWSIAMInstanceProfile_importBasic (25.08s)
=== RUN TestAccAWSIAMInstanceProfile_basic
--- PASS: TestAccAWSIAMInstanceProfile_basic (22.40s)
=== RUN TestAccAWSIAMInstanceProfile_withRoleNotRoles
--- PASS: TestAccAWSIAMInstanceProfile_withRoleNotRoles (22.63s)
=== RUN TestAccAWSIAMInstanceProfile_missingRoleThrowsError
--- PASS: TestAccAWSIAMInstanceProfile_missingRoleThrowsError (4.02s)
=== RUN TestAccAWSIAMInstanceProfile_namePrefix
--- PASS: TestAccAWSIAMInstanceProfile_namePrefix (22.18s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 96.349s
```
* Update iam_instance_profile.html.markdown
- When creating an `iam_instance_profile` you will receive an error if you have multiple roles defined but have not increased your AWS limit for the number of roles you can assign to an `iam_instance_profile`.
- See more on defaults: http://docs.aws.amazon.com/IAM/latest/UserGuide/reference_iam-limits.html
In this example, principal "AWS": "*" tells IAM that any user in the world can assume that role as long as they know the account ID + role name.
In my testing, "Service": "ec2.amazonaws.com" is sufficiently permissive to allow the instance_profile to work without allowing global accesses.
