[BUGFIX] Tests: Improve Mocking in ext:extbase

Unittests reveal some warnings which are caused by incomplete mocking.

Change-Id: Iee09220d675335aeadd286c2d4544d53c981016f
Resolves: #56700
Related: #51436
Releases: 6.2
Reviewed-on: https://review.typo3.org/28365
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn