patch 9.1.1517: filetype: autopkgtest files are not recognized

patch 9.1.1517: filetype: autopkgtest files are not recognized

Problem:  filetype: autopkgtest files are not recognized
Solution: detect */debian/tests/control files as autopkgtest filetype
          (James McCoy)

Autopkgtest is a Debian tool for testing installed versions of packages
when other, related packages are updated.

Reference:
- https://www.debian.org/doc/debian-policy/autopkgtest.txt

related: #17679

Signed-off-by: James McCoy <jamessan@jamessan.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>