MDEV-15919 lower_case_table_names does not behave as expected

followup for e31e697f

Fix the test not to fail on Mac OS X
(lower_case_table_names=0 prevents mysqld from starting on case insensitive
filesystem)

mysql-test/suite/rpl/t/rpl_15919-master.opt

---lower_case_table_names=0

mysql-test/suite/rpl/t/rpl_15919.test

---source include/master-slave.inc
+--source include/have_case_sensitive_file_system.inc
 --source include/have_innodb.inc
+--source include/master-slave.inc
+
 --connection master
 create table RPL(a int);
 insert into RPL values(1);