[TASK] Fix functional tests in WorkspaceServiceTest

Refactor WorkspaceServiceTest to reflect recent changes
in functional testing.
Enable test so they will be run in Travis.
Still 2 tests are skipped and need further review,
but it can be done in the separate change.

Resolves: #51164
Releases: 6.2
Change-Id: I074629d877b6a4d336bd21aacd20268bf4746811
Reviewed-on: https://review.typo3.org/23185
Reviewed-by: Stefan Neufeind
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn