D31084 put atf-pytest-wrapper in the /usr/tests. It is causing problems with distribution target.
While this can be fixed by altering DISTRIBUTION, ${PACKAGE}FILESDIR and a couple of other variables in the Makefile, it doesn't look like a proper way of doing things.
Target Makefile would need to replicate some logics from bsd.test.mk which is not desired.

Instead, switch to a cleaner approach by moving this wrapper to the atf-sh wrapper in libexec/atf.
This way it's logically tied to our in-base version of atf and constantly installed with other atf wrappers to /usr/libexec.