Restore RI trigger sanity check

I unnecessarily removed this check in 3de241db because I
misunderstood what the final representation of constraints across a
partitioning hierarchy was to be.  Put it back (in both branches).

Discussion: https://postgr.es/m/201901222145.t6wws6t6vrcu@alvherre.pgsql

src/backend/utils/adt/ri_triggers.c

@@ -1739,6 +1739,13 @@ ri_FetchConstraintInfo(Trigger *trigger, Relation trig_rel, bool rel_is_pk)
 			elog(ERROR, "wrong pg_constraint entry for trigger \"%s\" on table \"%s\"",
 				 trigger->tgname, RelationGetRelationName(trig_rel));
 	}
+	else
+	{
+		if (riinfo->fk_relid != RelationGetRelid(trig_rel) ||
+			riinfo->pk_relid != trigger->tgconstrrelid)
+			elog(ERROR, "wrong pg_constraint entry for trigger \"%s\" on table \"%s\"",
+				 trigger->tgname, RelationGetRelationName(trig_rel));
+	}
 
 	if (riinfo->confmatchtype != FKCONSTR_MATCH_FULL &&
 		riinfo->confmatchtype != FKCONSTR_MATCH_PARTIAL &&