[BUGFIX] Mock locked records for DataProviderTest

The DataProviderTest calls BackendUtility::isRecordLocked
statically. We cannot mock that call, but we can
"mock" a locked record so that BackendUtility::isRecordLocked
does not query the database.

Resolves: #56472
Releases: 6.2
Change-Id: I268a7a900a0f2dcbf248f6a4d856354c7b1cdcd6
Reviewed-on: https://review.typo3.org/27975
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel