service(8): Reset OPTIND properly now that we're parsing args twice

r328032 introduced a second round of argument parsing to proxy the request
through to a jail as needed, but failed to reset OPTIND before getting to
the second round of parsing to allow other flags to be set.

Reported by:	Oleg Ginzburg <olevole olevole ru>

usr.sbin/service/service.sh

@@ -79,6 +79,7 @@ if [ -n "$JAIL" ]; then
 	exit $?
 fi
 
+OPTIND=1
 while getopts ${accepted_argstr} COMMAND_LINE_ARGUMENT ; do
 	case "${COMMAND_LINE_ARGUMENT}" in
 	e)	ENABLED=eopt ;;