Bug #31240 load data infile replication between (4.0 or 4.1) and 5.1 fails

Overriding a default value of --secure-file-priv on pb.mtr with a value allowable 
the test to pass on pb.

mysql-test/suite/rpl/t/rpl_cross_version-master.opt:
  Overriding a default value of --secure-file-priv with a value allowable the test to pass on pb.

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

---replicate-same-server-id --relay-log=slave-relay-bin
+--replicate-same-server-id --relay-log=slave-relay-bin --secure-file-priv=$MYSQL_TEST_DIR