Continuation of the previous cset: rename sysvar's test, too.

use_direct_writes was renamed to use_direct_io_for_flush_and_compaction

storage/rocksdb/mysql-test/rocksdb_sys_vars/r/rocksdb_use_direct_io_for_flush_and_compaction_basic.result

+SET @start_global_value = @@global.ROCKSDB_USE_DIRECT_IO_FOR_FLUSH_AND_COMPACTION;
+SELECT @start_global_value;
+@start_global_value
+0
+"Trying to set variable @@global.ROCKSDB_USE_DIRECT_IO_FOR_FLUSH_AND_COMPACTION to 444. It should fail because it is readonly."
+SET @@global.ROCKSDB_USE_DIRECT_IO_FOR_FLUSH_AND_COMPACTION   = 444;
+ERROR HY000: Variable 'rocksdb_use_direct_io_for_flush_and_compaction' is a read only variable

storage/rocksdb/mysql-test/rocksdb_sys_vars/r/rocksdb_use_direct_writes_basic.result

-SET @start_global_value = @@global.ROCKSDB_USE_DIRECT_WRITES;
-SELECT @start_global_value;
-@start_global_value
-0
-"Trying to set variable @@global.ROCKSDB_USE_DIRECT_WRITES to 444. It should fail because it is readonly."
-SET @@global.ROCKSDB_USE_DIRECT_WRITES   = 444;
-ERROR HY000: Variable 'rocksdb_use_direct_writes' is a read only variable

storage/rocksdb/mysql-test/rocksdb_sys_vars/t/rocksdb_use_direct_writes_basic.test → storage/rocksdb/mysql-test/rocksdb_sys_vars/t/rocksdb_use_direct_io_for_flush_and_compaction_basic.test

 --source include/have_rocksdb.inc
 
---let $sys_var=ROCKSDB_USE_DIRECT_WRITES
+--let $sys_var=ROCKSDB_USE_DIRECT_IO_FOR_FLUSH_AND_COMPACTION
 --let $read_only=1
 --let $session=0
 --source include/rocksdb_sys_var.inc