[BUGFIX] Incomplete mocking in Bootstrap test

ReflectionService is not properly mocked in one of the extbase
bootstrap tests and can raise a warning (in travis) that some
related database table does not exist.

Change-Id: Iadf021887b1636d0147ef5d75e63edf290bfeceb
Releases: 6.2, 6.1
Resolves: #47715
Related: #39140
Reviewed-on: https://review.typo3.org/20326
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn