ovn-nbctl: Detect unrecognized short options in server mode.

ovn-nbctl: Detect unrecognized short options in server mode.

Because getopt() will set optopt for both known and unknown options,
we need to differentiate between them ourselves by checking if we
know the option. Do that by looking up its value.

Also, because we are using GNU extensions to getopt(), we need to be
resetting getopt() state by setting optind to 0 instead of 1 as
pointed out in NOTES in getopt(3) man-page. Not doing so results in
invalid reads and optopt being set to a garbarge value.

Fixes: 3ec06ea9c668 ("ovn-nbctl: Initial support for daemon mode.")
Signed-off-by: Jakub Sitnicki <jkbs@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>