nuageinit: Add doas support
- Set mode of etc directory to 0755.
- Use user.localbase sysctl instead of /usr/local.
- Add test case for doas.
- Set ${LOCALBASE} instead of /usr/local in nuageinit(7) man page.
Reviewed by: bapt@
Approved by: bapt@
Differential Revision: https://reviews.freebsd.org/D52437
(cherry picked from commit 9a829e865697e623a046800545be7781a117125e)