Fix KDC worker process argument parsing

Fix KDC worker process argument parsing

To create worker processes, the KDC shuts down realms, forks off the
worker processes, then reinitializes realms in each child.
Reinitializing realms requires making a second pass over the
command-line arguments.  To do this with getopt, optind must be
reinitialized to 1 for each pass; otherwise, no options will be seen
the second time around.

ticket: 7945
target_version: 1.12.2
tags: pullup