Use the portable form of INSTALL PLUGIN in rpl_mdev359.test

mysql-test/suite/rpl/r/rpl_mdev359.result

 include/master-slave.inc
 [connection master]
 CREATE TABLE t1 (a INT) ENGINE=MyISAM;
-INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so';
+INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master';
 SET GLOBAL rpl_semi_sync_master_enabled = ON;
 SET DEBUG_SYNC = "rpl_semisync_master_commit_trx_before_lock SIGNAL m1_ready WAIT_FOR m1_cont";
 INSERT INTO t1 SELECT * FROM t1;

mysql-test/suite/rpl/t/rpl_mdev359.test

@@ -13,7 +13,7 @@
 # the code, disable the semisync, and then continue the paused thread.
 
 CREATE TABLE t1 (a INT) ENGINE=MyISAM;
-INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so';
+INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master';
 SET GLOBAL rpl_semi_sync_master_enabled = ON;
 --connection master1
 SET DEBUG_SYNC = "rpl_semisync_master_commit_trx_before_lock SIGNAL m1_ready WAIT_FOR m1_cont";