erp5_base: recalculate user group after closing the assignment

If user group are recalculated before changing the workflow state, it will only return the same security group
See nexedi/erp5@c00c3636
8 jobs for wip in 0 seconds
Status Job ID Name Coverage
  External
failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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failed ERP5.UnitTest-Romain

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