Fix rocksdb.tbl_opt_data_index_dir on a mac

Part #2: also replace error text in SHOW WARNINGS

storage/rocksdb/mysql-test/rocksdb/t/tbl_opt_data_index_dir.test

@@ -20,11 +20,13 @@ DROP TABLE IF EXISTS t1;
--replace_result error: error
--error ER_CANT_CREATE_TABLE
CREATE TABLE t1 (a INT PRIMARY KEY, b CHAR(8)) ENGINE=rocksdb DATA DIRECTORY = '/foo/bar/data';
--replace_result error: error
show warnings;

--replace_result error: error
--error ER_CANT_CREATE_TABLE
CREATE TABLE t1 (a INT PRIMARY KEY, b CHAR(8)) ENGINE=rocksdb INDEX DIRECTORY = '/foo/bar/index';
--replace_result error: error
show warnings;

#
@@ -41,6 +43,7 @@ CREATE TABLE t1 (id INT NOT NULL PRIMARY KEY) ENGINE=rocksdb PARTITION BY RANGE
        DATA DIRECTORY =  '/foo/bar/data/',
    PARTITION P2 VALUES LESS THAN (MAXVALUE)
);
--replace_result error: error
show warnings;

--replace_result error: error
@@ -53,4 +56,5 @@ CREATE TABLE t1 (id int not null primary key) ENGINE=rocksdb PARTITION BY RANGE
       INDEX DIRECTORY =  '/foo/bar/data/',
   PARTITION P2 VALUES LESS THAN (MAXVALUE)
);
--replace_result error: error
show warnings;