make-ssl-cert: expiration-day (-x option) is wrongly handled, if set it is 3 days instead of the value given

[jpph]

Expiration-day is wrongly handled, if set it is 3 days instead of the value given. In the script ${OPTIND} should be replaced by ${OPTARG}

[Paride Legovini (paride)]

I quickly tried to reporoduce this by hacking make-ssl-cert to print $opt_expiration_days after opts are parsed and exit (to avoid looking at what the rest of the script does), and I can reproduce the issue.

The suggested fix appears to work.