AWS user export only supports a max of 100 users

[iamjoeker]

The AWS user export sets a max item count of 100 but does not use the paging API to continue exporting if more than 100 users are defined in IAM. The IsTruncated property on the result should be checked to see if there are more users. This could also be a problem if fewer than 100 users exist as the SDK docs indicate ListUsers may return fewer than MaxItems results even if more are available.

See https://docs.aws.amazon.com/sdk-for-go/api/service/iam/#ListUsersInput