Add directories that is installed as part of bsdconfig.

These are included unconditionally for now because bsdconfig
is currently installed unconditionally.

This fixes 'make -j 17 installworld' caused by a race
condition.

MFC candidate.

(cherry picked from commit 4d90834da43f660fc930f3946a35b5cb4e9b4e55)
Add missing libexec/bsdconfig subdirectories

(cherry picked from commit 8669111217d1a782a1a6b059c31e37bb65d9fd0c)