Testcase fixes

The example from `software/slapos-sr-testing/README.md` in slapos repository uses a path with `~` for shared parts, but this was not supported.

Also, what was not supported is to use `setUpModule` more than once, but erp5 SR tests are starting to do this.

See merge request !196
4 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
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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