cubicweb-dataio #4123136 is_relation table content is wrong [validation pending]

prioritynormal
typebug
done in0.6.0
load0.500
load left0.000
closed by#6f0aed996f6f [dataimport] Fix entity type metadata creation (closes #4123136)
patch[dataimport] Fix entity type metadata creation (closes #4123136) [rejected][dataimport] Fix entity type metadata creation (closes #4123136) [applied]