colrm(1): Replace magic exit codes with standard macros

Signed-off-by: Faraz Vahedi <kfv@kfv.io>
Reviewed by: markj, oshogbo
MFC after: 1 week
Pull Request: https://github.com/freebsd/freebsd-src/pull/1496

(cherry picked from commit fc26f24b3ef276b2a9f73c9778aecff7377b1aeb)