The Id wasn't being set until after the Read func returned from the API.
I needed to move that Id set up until just after the Create response
returned
The same Id's have been set - username
```
make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSUser_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /vendor/)
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSUser_
-timeout 120m
=== RUN TestAccAWSUser_importBasic
--- PASS: TestAccAWSUser_importBasic (14.24s)
=== RUN TestAccAWSUser_basic
--- PASS: TestAccAWSUser_basic (24.99s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 39.261s
```