[BUGFIX] Tests: Incomplete mocking in be_user

ModuleDataStorageServiceTest now mocks $GLOBALS['BE_USER']
to not rely on instantiation of this global.

Change-Id: I5ab6b962d95f2ab183dfc1b1b53dea7deaa464c5
Resolves: #56687
Related: #51436
Releases: 6.2
Reviewed-on: https://review.typo3.org/28196
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
[BUGFIX] Resolve incomplete mocking for sysext:fluid

Some Tests in sysext:backend rely on an existing BackendUserAuth object.
In order to decouple the tests from the TYPO3 Environment,
those are mocked now.

Change-Id: Ibfd9de2f5a7673eecca61c35e59852017edd2f0d
Resolves: #56688
Relates: #51436
Releases: 6.2
Reviewed-on: https://review.typo3.org/28198
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters