bsnmp: Fix incorrect use of libpfctl

When we introduced libpfctl in bnsmpd this was done incorrectly, and a
GETRULE call was replaced by pfctl_add_rule().
Change it to pfctl_get_rule().

Reviewed by:	donner
MFC after:	3 days
Sponsored by:	Rubicon Communications, LLC ("Netgate")

usr.sbin/bsnmpd/modules/snmp_pf/pf_snmp.c

@@ -1530,8 +1530,8 @@ pfl_scan_ruleset(const char *path)
 
 	for (nr = pr.nr, i = 0; i < nr; i++) {
 		pr.nr = i;
-		if (pfctl_add_rule(dev, &rule, pr.anchor, pr.anchor_call,
-		    pr.ticket, pr.pool_ticket)) {
+		if (pfctl_get_rule(dev, pr.nr, pr.ticket, pr.anchor,
+		    PF_PASS, &rule, pr.anchor_call)) {
 			syslog(LOG_ERR, "pfl_scan_ruleset: ioctl(DIOCGETRULE):"
 			    " %s", strerror(errno));
 			goto err;