tests: Make role_category_list argument actually a list

The setter does this already so no change is expected, but these are API
misuses and they just look wrong.
12 jobs for master in 0 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

01:45:07

failed ERP5.UnitTest-Master

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failed ERP5.UnitTest-Zope2

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

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failed Wendelin.UnitTest-Master

01:18:25

passed ERP5.CodingStyleTest-Master

00:54:40

passed ERP5.UnitTest-Master

01:48:44

failed ERP5.UnitTest-Zope2

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passed SlapOS.Eggs.UnitTest-Master.Python2

01:57:21

passed SlapOS.Eggs.UnitTest-Master.Python3

01:42:31

passed Wendelin.UnitTest-Master

00:34:35