Tags attached to an IAM user are not saved. Create a user with attached tags. The response from the create user doesn't include the tags and when you run a GetUser the tags are not included.
```
aws-sdk-swift % aws --endpoint-url http://localhost:4593 iam create-user --user-name test-user --tags Key=test,Value=hello
```
produces output
```
{
    "User": {
        "Path": "/",
        "UserName": "test-user",
        "UserId": "peldynzrvm2tofi6nmmr",
        "Arn": "arn:aws:iam::000000000000:user/test-user",
        "CreateDate": "2019-10-23T08:46:31.305Z"
    }
}
```
The GetUser call produces exactly the same output
```
aws --endpoint-url http://localhost:4593 iam get-user --user-name test-user
```


I am running localstack as follows
```
docker run -d -p 4593:4593 -e SERVICES='iam' localstack/localstack
```
import re
from requests.models import Request
from localstack.constants import TEST_AWS_ACCOUNT_ID, MOTO_ACCOUNT_ID
from localstack.utils.aws import aws_stack
from localstack.utils.common import to_str
from localstack.services.generic_proxy import ProxyListener
class ProxyListenerIAM(ProxyListener):
    def forward_request(self, method, path, data, headers):
        if method == 'POST' and path == '/':
            data = self._reset_account_id(data)
            return Request(data=data, headers=headers, method=method)
        return True
    def return_response(self, method, path, data, headers, response):