[#1462] Run elevated tests on a computer join to a domain.

Problem description
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Elevated tests are not running on a computer that is joined to a domain.


Changes description
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The main problem was 'NetUserChangePassword' which has a different syntax than the others Net* functions. The first argument should be the computer were the user account for which we need to change the password is stored and not 'None'.


How to try and test the changes
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reviewers @adiroiban 


Look at the code. Run the tests on a slave that is joined on a domain (win-dc-x64). The tests should pass.