SET tx_isolation cancels out strict_multi_stmt and strict_sp_calls

If readwritesplit is configured with strict_multi_stmt or strict_sp_calls and a SET tx_isolation='repeatable-read' is executed, the effects of strict_multi_stmt and strict_sp_calls are canceled out. The following test case should return the same server_id value as long as the session is alive but it may return a server_id from a replica.

delimiter $$ ;

SELECT @@server_id AS 'before multistmt' $$

DO 1; DO 2; $$

SELECT @@server_id AS 'after multistmt' $$

SET tx_isolation='read-committed' $$

SELECT @@server_id AS 'after tx_isolation' $$