update usage with coldplug-only info

[suedi]

I saw info about --coldplug-only was missing in usage message.

Are you going to keep -1 ,--once also, it was my impression you would not?

I keep forgetting what it was so would be helpful to just do vdevd --help and find out. ( -1 is very easy to remember so I hope you keep that, -n is not as intuitive)

[jcnelson]

Yes, I intend to keep both options. I'll add the relevant information to the --help section as well.

[suedi]

Just to push you to commit so I can close of this rather silly bug. (a bit silly by me reporting it I mean)

in config.c-->vdev_config_usage()

int vdev_config_usage( char const* progname ) {
   fprintf(stderr, "\
...
   -l, --log-file LOGFILE_PATH\n\
                  Path to which to log information.\n\
                  Pass 'syslog' to log to syslog, instead of a logfile.\n\
                  \n\
   -1, --once \n\
       --coldplug-only \n\
                  Exit once all extant devices have been processed.\n\
                  \n\
   -f, --foreground\n\
                  Run in the foreground; do not daemonize.\n\
                  \n\
...

[jcnelson]

Not silly at all! I can merge it directly, or if you want, you can send it as a PR and it'll reflect your contribution in the project's commit history. Your call :)

[suedi]

I'll take the contribution - sent you a PR

closing...