In mod.php the bootstrap is instanciated without using the
objectManager, thus it's not possible to overwrite it.

Change-Id: I4720172ef4b602fdb31c3a58112c03f0d6673db2
Fixes: #35955
Releases: 6.0
Reviewed-on: http://review.typo3.org/10387
Reviewed-by: Oliver Klee
Tested-by: Oliver Klee
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn