util: use safe variant or xml_marshaller

Also change places where xml_marshaller were used directly to always use
the wrapper from utils (except in tests for simplicity)
11 jobs for fix/xml_marshaller_safe in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS.Eggs.UnitTest-Jerome.Python2

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:10:46

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:33:04

failed SlapOS.Eggs.UnitTest-Jerome.Python2

01:19:53

failed SlapOS.Eggs.UnitTest-Jerome.Python2

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:24:36

failed SlapOS.Eggs.UnitTest-Jerome.Python2

passed SlapOS.Eggs.UnitTest-Jerome.Python2

00:24:32

failed SlapOS.Eggs.UnitTest-Jerome.Python2

00:45:58

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:16:23

passed SlapOS.Eggs.UnitTest-Jerome.Python3

00:12:48