libpfctl: fix a mismerge breaking label addition

This code was supposed to apply to pfctl_add_eth_rule() but instead
applied to pfctl_add_rule() for otherwise interesting reasons.  Since
pfctl_add_eth_rule() uses "nvl" and pfctl_add_rule() uses "nvlr" but
also has "nvl" this compiled fine but still broke the label set.

The bit that is most intriguing is that pfctl_add_eth_rule() doesn't
even exist on stable/13 and that this wasn't caught by the existing
tests.

lib/libpfctl/libpfctl.c

@@ -643,7 +643,7 @@ pfctl_add_rule(int dev, const struct pfctl_rule *r, const char *anchor,
 	labelcount = 0;
 	while (labelcount < PF_RULE_MAX_LABEL_COUNT &&
 	    r->label[labelcount][0] != 0) {
-		nvlist_append_string_array(nvl, "labels",
+		nvlist_append_string_array(nvlr, "labels",
 		    r->label[labelcount]);
 		labelcount++;
 	}