slapos.core: Release 1.6.8

This is a fixup release, as 1.6.7 was missing important changelog.
8 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS-Master.UnitTest-Master

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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.Python3

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passed SlapOS.Eggs.UnitTest-Master.Python3

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passed SlapOS.Eggs.UnitTest-Master.Python3

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