erp5_core: Make two queries in Base_getRelatedDocumentList

See merge request !1373
13 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed ERP5.CodingStyleTest-Master

01:07:55

passed ERP5.PerformanceTest-Master

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failed ERP5.UnitTest-Master

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failed ERP5.UnitTest-Master.Medusa

02:05:41

passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python2

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passed SlapOS.Eggs.UnitTest-Master.Python3

passed SlapOS.Eggs.UnitTest-Master.Python3

00:51:09

passed SlapOS.Eggs.UnitTest-Master.Python3

01:02:28

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:50