tftpd: Make the -d option behave as documented.

[des]

Summary

Sponsored by: Klara, Inc.

[markj]

libexec/tftpd/tftpd.c

157

According to the documentation, these += and |= should be simple assignments. Maybe the documentation should be updated instead.

[des]

libexec/tftpd/tftpd.c

157

I don't agree with that interpretation, at best I'd say it's vague on that point. This is the behavior that makes sense to me and debug_finds() gives me a headache so I'd rather leave well enough alone.