This patch changes the module to use the sdk proxy layer and does some
general refactoring to simplify the code. It will no longer fail if
no password is supplied since it is perfectly fine to create a user
with an password.

Renamed the test role from user to identity_user to match the module
name

Change-Id: I97ee9b626f269abde3be7b2b9211d2bb5b7b3c26