Add integration tests for CLI import as (rebased onto develop)



This is the same as gh-2570 but rebased onto develop.

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This PR adds:
- a passing integration test for `bin/omero import --sudo=root` command introducded in 5.0.2
- a failing integration test for the command above in multi-group context with the `-g` option (see http://trac.openmicroscopy.org.uk/ome/ticket/12288)