MXS-2043 Create test that exposes problem

A statement like

    SELECT a FROM tbl FOR UPDATE;

should be classified like QUERY_TYPE_WRITE so as to be sent
to master.

query_classifier/test/input.sql

@@ -24,3 +24,4 @@ SELECT IS_FREE_LOCK('lock1');
 SELECT IS_USED_LOCK('lock1');
 SELECT RELEASE_LOCK('lock1');
 deallocate prepare select_stmt;
+SELECT a FROM tbl FOR UPDATE;