dict-sql: Fix flushing

Remove flushing from set, and add it to unset. Fixes
signal 11 crash caused by infinite recursion.

src/lib-dict/dict-sql.c

@@ -1064,11 +1064,6 @@ static void sql_dict_set_real(struct dict_transaction_context *_ctx,
 		return;
 	}
 
-	if (ctx->prev_inc_map != NULL)
-		sql_dict_prev_inc_flush(ctx);
-	if (ctx->prev_set_map != NULL)
-		sql_dict_prev_set_flush(ctx);
-
 	field.map = map;
 	field.value = value;
 
@@ -1103,6 +1098,8 @@ static void sql_dict_unset(struct dict_transaction_context *_ctx,
 
 	if (ctx->prev_inc_map != NULL)
 		sql_dict_prev_inc_flush(ctx);
+	if (ctx->prev_set_map != NULL)
+		sql_dict_prev_set_flush(ctx);
 
 	map = sql_dict_find_map(dict, key, &values);
 	if (map == NULL) {