Rename the 'path' argument of the MasterShellCommand 'workdir'
Make the tests more realistic
Update doc and release note
Merge pull request #1295 from benallard/mastershell_workdir

Rename the 'path' argument of the MasterShellCommand 'workdir'

- All other steps take a workdir
- The path argument is not mentioned in the doc
  - Even worse, the doc has an example: command="cd dir; do stuff"
- As the test show, the one that wrote it believed it would become the PATH.