Add failing test for #13369

After introducing 50311f1 a regression was introduced: routes with
trailing slash are no longer recognized properly. This commit provides a
failing test for this situation.
Revert "Don't remove trailing slash from PATH_INFO for mounted apps"

The revert is needed because of a regression described in #13369, routes
with trailing slash are no longer recognized properly.

This reverts commit 50311f1391ddd8e0349d74eb57f04b7e0045a27d.