MFC r304570,r321235:

r304570 (by trasz):

Add the "-n" flag to cron(8), to prevent it from daemonizing.
This makes it possible to use it with external supervisors.
The "-n" flag name is compatible with Linux, NetBSD, and OpenBSD.

r321235:

Fix trivial whitespace bug introduced in usage message changes for -n
support (r304570).