Add test for creating user with non-unique uid.
Add test for creating user with non-unique uid.

fabtools/fabtools,hagai26/fabtools,davidcaste/fabtools,prologic/fabtools,n0n0x/fabtools-python,badele/fabtools,pombredanne/fabtools,AMOSoft/fabtools,ahnjungho/fabtools,wagigi/fabtools-python,sociateru/fabtools,bitmonk/fabtools,ronnix/fabtools